Public perception of the patent system has swung widely over the years from highs, such as those in the late nineteenth century when Mark Twain could write "a country without a patent office and good patent laws was just a crab and couldn't travel anyway but sideways or backwards"  to lows in the mid twentieth century when it could be written "the only patent that is valid is one which this (the Supreme) Court has not yet been able to get its hands on."  The value and philosophical basis underpinning the patent system has been a matter for debate over the years.
Patent Systems in Medieval Times
In medieval times, the grant of exclusive rights "monopolies" by the sovereign had been a convenient way in which the sovereign could raise money without the need to resort to taxation. Such grants were common in many European countries. Some of these, for example in mining regions or in respect of production of certain textiles seem to have had a relation to innovations. Although there seems to have been an earlier law directed specifically at inventions relating to the manufacture of silk, the first law providing for the grant of exclusive rights for limited periods to the makers of inventions in general as a deliberate act of economic policy seems to have been in Venice in 1474. It does not seem coincidental that this was during a long war between Venice and the Turks during which Venice lost most of its trading empire in the Eastern Mediterranean and consequently had to refocus its economy on manufacture rather than trade. Indeed, as Venice's domination of trade with the East weakened, it adopted a number of measures to establish and maintain a preeminence in manufacture including laws prohibiting emigration of skilled artisans and the export of certain materials, while at the same time encouraging the immigration of skilled workers from other countries, for example by a tax holiday for two years after their arrival in Venice.
Towards the end of Elizabeth's reign the English courts, probably at least to some extent noting developments on the Continent started to restrict the rights ofthe sovereign to grant monopolies unless they were for the introduction of anew industry to the country.
In 1624 as part of the skirmishing between Parliament and the Crown leading up to the English Civil War, the English Parliament passed the statute of monopolies. This had the effect of limiting the power of the Crown to the grant of monopolies to making such grants only to inventions for limited periods (14 years - the duration of two training periods for craft apprentices) and most importantly only for "manners of new manufacture" that were introduced into the realm by the recipient of the monopoly. Such grants were, however, conditioned on their not being "mischievous to the state" (for example by raising prices of commodities) or "generally inconvenient"
As noted above the original English approach, which was followed in the American Constitution, was to place emphasis on the advantage to society as a whole of developing new inventions. Section 1 of the French law of 1791 took a somewhat different approach: "All new discoveries are the property of the author; to assure the inventor the property and temporary enjoyment of his discovery, there shall be delivered to him a patent for five, ten or fifteen years". The emphasis here was on the inventor having property in his discovery - an emphasis on the rights in the invention rather than on the benefits to society. Today this approach is of limited importance in the patent field but it is still significant in the area of copyright - where the Anglo Saxon approach is focussed heavily on the bundle of economic rights associated with control over whether others are entitled to copy a work, whereas the French approach focusses more heavily on the moral rights of authors - a fact that is emphasized by the fact that the word generally used as the French translation of the word "Copyright" is "droit d'auteur" (literally Author's Rights).
Modern thinking on the rationale for a patent system effectively sees this as a contract between the invention and society at large. This was well expressed in a report to the French Chamber of Deputies in the debates preceding adoption of the French Patent Law of 1844 (a law that remained in effect with little change up to the 1960's):
"Every useful discovery is, in to Kant's words 'the presentation of a service rendered to Society'. It is, therefore, just that he who has rendered this service should be compensated by Society that received it. This is an equitable result, a veritable contract or exchange that operates between the authors of a new discovery and Society. The former supply the noble products of their intelligence and Society grants to them in return the advantages of an exclusive exploitation of their discovery for a limited period".
As Abraham Lincoln once put it "The Patent System added the fuel of interest to the fire of genius."
This paper attempts to summarize the way in which the patent system has developed in the United States, noting the different attitudes that have prevailed at different times and the effects that these have had on development of the patent law.
The United States Constitution, on which U.S. Patent Law depends, was drafted at the height of the industrial revolution at a time when the impact of patents was first being seriously felt in England. Additionally, while the Constitution was being drafted in Philadelphia, John Fitch’s steam boat was undergoing trials on the Delaware River and the Constitutional Convention apparently adjourned one afternoon to watch them. A pro-patent climate endured in the United States through much of the nineteenth century leading to the comments by President Lincoln and Mark Twain noted above.  However, the last two decades of the nineteenth century and the twentieth century have seen a number of climate changes. In the last two decades of the nineteenth century there was a period of economic depression and increasing concern about the power of "big business" leading to the passage of the Sherman Antitrust Act in 1890. This climate was reflected in the patent field by an increasing tendency of the courts to hold patents invalid. By the late 1890's the depression had run its course and patents came back into favor with the reviving economy.
In general the twentieth century has seen a dynamic interrelationship between the patent system and the application of antitrust laws. Although the first antitrust law, the Sherman Act, was enacted in 1890, the courts did not start to give it teeth until Theodore Roosevelt‘s administration (1901-1909). It was not until the 1930's that the patent system started to come under attack, being viewed as assisting in the maintenance of monopolies that were seen as being at least a contributing factor to the economic misery of the thirties. This skepticism about the patent system survived World War II and blossomed again in the depressed economic conditions of the 1970's, a period of strong anti-trust enforcement.
In the early 1980's, the thinking of the Chicago School of economists came to the fore and with the election of President Reagan enthusiasm for antitrust enforcement went out of fashion. At about the same time the Court of Appeals for the Federal Circuit was created at least in part to remedy a scandalous disarray between the regional circuit Courts of Appeal in dealing with patent cases. The new court initially seemed pro-patent in its attitude and this has resulted in a generally more favorable attitude to the value of patents throughout American business.  One manifestation of this change has been the court's assertion that the patent statute means what it says when stating that "a patent shall be presumed valid.  The court has held that anyone challenging the validity of a patent needs "clear and convincing" evidence to succeed.  This contrasts with the normal standard of proof in civil cases in which a party asserting a cause need only establish his case on the balance of probabilities. On the other hand more recently decisions of the court have cautioned against giving too wide an interpretation to patents and reiterated the importance of the public having a clear understanding of what does or does not fall within the ambit of any given patent. Thus over the past two decades patents have been back in favor, but the pendulum will probably swing again.
The earliest grants of a patent for an invention in what is now the United States seems to have been by the Massachusetts Bay Colony in the 1640's. Although pre-independence patent custom in the American colonies owes much to the English Statute of Monopolies of 1624, which restricted the right of the crown to grant monopolies so that henceforth they could be granted only for a limited period and only for manners of new manufacture.  The Statute of Monopolies was never made directly applicable to the American colonies.  During the period of the Confederation after independence had been achieved but before the adoption of the Federal Constitution of the United States, most of the states had their own patent laws, although only that of South Carolina specifically set out a provision granting inventors an exclusive privilege of using their new machines for a defined period (14 years). However, as noted by James Madison in the Federalist "the States cannot separately make effectual provision" for the protection of invention and so in drafting the Constitution of the United States, responsibility for providing such protection was entrusted to the Congress of the United States.
The Constitutional basis for federal patent and copyright systems is to be found in the Constitution of the United States Article 1, Section 8, clause 8 which states:
Congress shall have power ... to promote the progress of science and useful arts by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries.
Federal patent laws have existed since 1790
The first United States Patent Act, that of 1790 was a short act of seven sections only entitled "An act to promote the Progress of Useful Arts".  Under its terms any two of the Secretary of State, the Secretary of War and the Attorney General were empowered to grant patents for terms of up to fourteen years for inventions that were "sufficiently useful and important" provided that the grantee submitted a specification describing the invention (and where appropriate a model thereof) to the Secretary of State at the time of the grant.
In 1793 this act was repealed and replaced by a slightly longer act, the drafting of which is largely attributed to Thomas Jefferson, who was at the time Secretary of State and therefore intimately involved in the administration of the 1790 Act. The Act is notable for its definition of what constitutes patentable subject matter in the United States, which definition is almost unchanged up to now:
any new and useful art, machine, manufacture or composition of matter and any new and useful improvement on any art, machine, manufacture or composition of matter. 
A short description had to be filed with the application. However, before grant could occur it was necessary to submit a written description of the invention and of the manner of using or process of compounding the same in such full, clear, and exact terms, as to distinguish the same from all other things before known and to enable any person skilled in the art or science of which it is a part, or with which it is most nearly connected, to make, compound and use the same".  Another notable feature of the law was its early recognition that one patent might have a dominating effect over another and it specifically set out the principle that securing a patent on a particular improvement of a previously patented invention did not give the patentee of the improvement patent any right to use the invention that was the subject of the original patent or vice versa.  However, the only examination of the application was a purely formal one.
Rights to patents under the 1793 Act were confined to citizens of the United States.
The 1793 Act was amended in 1800 to allow foreigners who had been resident in the United States for two years to obtain patents, subject to them making an oath that the invention in question had not to their knowledge or belief been known or used previously in the United States or abroad. This act also provided for the first time the possibility of an award of treble damages for patent infringement.
What was meant by the term "new" in the early statutes varied somewhat but after 1800 the courts considered simply whether the invention was known before the date on which the applicant for a patent claimed to have made his or her invention.  In 1829 the Supreme Court in the case of Pennock v. Dialogue recognized the potential dangers of such an approach which enabled the inventor to delay filing a patent application until competition was imminent and construed the statute so as to create a statutory bar to deny patent protection to one who had previously publicly used his invention.
In 1832 a new act expanded the category of potential patentees to cover all resident aliens who had declared an intention to become citizens of the United States, provided however, that any patents granted to the class of patentee become void if they did not work the invention publicly in the United States within one year of grant. It also became possible to obtain reissue of a patent to correct errors in it. 
In the same year the Supreme Court in Grant v. Raymond made it clear that failure to provide an adequate description of the invention was a defense which a defendant might use when sued for patent infringement, it being held that
as a preliminary to a patent a correct specification and description of the thing discovered (was required). This is necessary in order to give the public, after the privilege shall expire, the advantage for which the privilege is allowed and is the foundation of the power to issue the patent ...
A major review of the law was undertaken in 1836 in response to complaints about the grant of patents for things that lacked novelty. Under this revision the Patent Office was set up as part of the State Department and a specification had to be submitted to it and be examined for novelty before a patent would be granted. As a consequence, the provision of the 1793 Act requiring the inventor to distinguish his invention from the prior art was expanded to require the applicant to "particularly specify and point out the part, improvement or combination, which he claims as his own invention or discovery".  This provision is the antecedent for modern claim drafting worldwide. Other features of the 1836 law were to codify the law relating to statutory bars,  to clarify the law relating to cases of conflict between competing applications and to provide a mechanism for establishing this.  The Act also provided for the possibility of obtaining a seven year extension to the basic fourteen year term in certain circumstances. The 1836 Act also finally removed all limitations on the nationality or residence of those who could obtain United States patents. However, it did not end all discrimination on this score. U.S. citizens or residents intending to become citizens were charged $30.00, British subjects were charged $500.00 and all other foreigners $300.00. 
In1839 the law was amended to provide for a grace period (of two years) forpublication or use of the invention by the applicant before filing his or her patent application.  The act also provided for an appeal from rejection of a patent application by the Patent Office to the Chief Justice of the District of Columbia. 
In 1842 a statute was passed to provide for the grant of patents for "any new and original design for a manufacture or for printing on a fabric. However, the right to obtain a patent for such a design was confined to U.S. citizens or residents who were intending to become citizens.
In 1849 responsibility for the Patent Office was transferred from the State Department to the Department of the Interior.
The next major step forward was the introduction of the concept that to be patentable an invention not only had to be new and useful but also non-obvious. This charge was effected by the courts rather than by statute, notably in the Supreme Court case of Hotchkiss v. Greenwood.
In 1861 a number of amendments were made. Among the more important were: the appointment of three examiners-in-chief to hear appeals from the primary examiners of any application that had been rejected twice ; the changing of the term of a utility patent to seventeen years from the date of grant ; and the provision of terms of three and a half, seven, or fourteen years for design patents at the choice of the applicant. Other features of the 1861 revision provided for the printing of copies of the description and claims of patents and a requirement that to secure damages for patent infringement either the patented article had to be marked as such or the infringer had to have been given notice in some other way of the existence of the patent.
The 1836 Act had provided that the applicant had the right to amend his or her specification if the Patent Office raised objections to it. In 1864 the Supreme Court imposed limits on this right to amend thereby forming the basis for the present rule that no new matter can be added during prosecution of an application. 
In 1866, the Supreme Court, in the case of Suffolk Mfg Co v. Hayden, laid the foundation for the modern doctrine of double patenting by holding that where the same inventor held two patents for the same invention, the second one was void.
In 1870 the legislation relating to patents was consolidated into a single act but without many significant amendments as to substance. Among the changes that were made were the following: removal of the requirement that if a patent had been granted abroad a U.S. application had to be filed within six months and replacement by a provision that the U.S. patent must expire at the same time as the foreign patent, subject to a maximum term of seventeen years from the grant of the U.S. patent; codification of a requirement that the specification described the best mode known to the applicant for "applying the principle" of his invention; set up a mechanism for resolving disputes as to who had first invented a particular invention (by creating the post of an "examiner in charge of interference"). It was also made clear that any public sale or use of the invention before the start of the two year grace period was destructive of novelty irrespective of whether that sale or use was by the applicant for the patent.
The 1870's and 80's were a period in which many international organizations were created. Among them was the Paris Convention for the Protection of Industrial Property which came into being in 1883 and which the United States joined in 1887. Its most important provision was to give applicants who were nationals or residents of one member state the right to file an application in their own country and then as long as an application was filed in another country that was a member of the treaty within a specified time, to have the date of filing in the home country count as the effective filing date in that other country.  The United States became a member of the Paris Convention on May 30, 1887. 
The 1890's saw two developments that, while not directly applicable to patents had a significant effect on the development of patent law: the passage of the Sherman Act in 1890 forming the basis for antitrust law and of the Evarts Act in 1891 creating the Circuit Courts of Appeals. In 1893 appeals from the Patent Office were transferred to the newly created Court of Appeal for the District of Columbia. 
In 1897 some of the statutory bars to the grant of a patent were revised: 1) if a foreign patent had already granted, a U. S application had to be made within seven months of filing of the foreign  and 2) it was made clear that prior knowledge or use was only a bar if it occurred in the United States before the applicant had made his invention.
In 1925 responsibility for the Patent Office was transferred to the Department of Commerce and Labor.
In 1929, appellate review of decisions of the Patent Office was transferred from the Court of Appeals for the District of Colombia to the newly created Court of Customs and Patent Appeals.
In 1930, the Plant Patent Act provided for the possibility of patent protection for asexually reproduced plants.
The 1930's and 40's (i.e. during the depression and World War II), was one in which the courts were generally not sympathetic to patents. Indeed in 1941, in Cuno Engineering v. Automatic Devices Corp. the Supreme Court suggested that to be patentable an invention must "reveal the flash of creative genius not merely the skill of the calling".
In 1939 the two year grace period that had existed since 1839 with respect to some statutory bars was reduced to one year on the ground that "under present conditions two years appears unduly long and operates as a handicap to industry."
In 1940, the duration of the grace period relating to acts of prior use or prior publication by the inventor which were to be excused as novelty-destroying acts was reduced from two years to one.
In 1946, the law was amended to overrule the Supreme Court's decision in Electric Storage Battery v. Shimadzu, which had applied the U.S. laws "first to invent" principle on a world wide basis. The statute confined the first to invent principle to situations where evidence of the invention could be found in the United States.
The basic structure of the present law was adopted in 1952.  The two major changes made at that time were to include in the statute for the first time a requirement that to be patentable an invention had not only to be novel, thereby codifying a century of case law, and to include a definition of infringement, which had hitherto been left to the courts.  Other changes included a minor change in the definition of what constituted patentable subject matter by replacing the eighteenth century word "art" by "process"; an express statement that when an invention involved a combination of elements it was possible to define such elements in functional terms (i.e. as a "means for" doing something) ; a relaxation of the formalities relating to applications by joint inventors and where an inventor cannot be found or refuses to apply for a patent even though bound by contract to do so; imposed a maximum time limit of two years within which to request reissue of a patent with broadened claims; abrogated the common law rule that a patent could not be partially valid and permitted actions to proceed on the basis of valid claims even if there were invalid claims in the same patent.
Since 1952, the law has been amended several times and has continued to develop by way of case law. Changes were relatively infrequent prior to the establishment of the Court of Appeals for the Federal Circuit in 1982. The increased interest in the patent system that at least in part led to the creation of this court has also resulted in an increased rate of change in the law. In part this has come from decisions of the new court, and the occasional intervention by the Supreme Court; other changes have come through legislation. The creation of the Federal Circuit Court of Appeals has, if nothing else, led to a more coherent body of law than existed previously. In its first decade the court seemed to focus heavily on issues of patent validity and to reverse the perception that had existed in the 1970's that few patents that came before the court were likely to be upheld. In its second decade, the perception was that, having established that patents needed to be taken seriously, the court’s focus shifted to try to ensure that the protection given by any one patent was not overly broad compared to the significance of the invention that had been made.
Legislative developments up to the mid 90's came largely to deal with specific and relatively minor issues that arose either as a result of case law or particular developments in the economy, most notably in the compromise reached in 1984 to make it easier to obtain approval from the U.S. Food and Drug Administration (FDA) for the sale of generic drugs after a patent had expired in return for the possibility of obtaining an extension to the term of a patent for a pharmaceutical invention to compensate the original inventor for the delays in marketing to which the original manufacturer had been subject while waiting for FDA approval. In 1994, a new trend started, at least in part as a result of renewed attempts at globalization of the patent system. In 1994, the law was amended to comply with a new international agreement that had been grafted on to the Uruguay round of amendments to the General Agreement on Tariffs and Trade. This agreement, commonly known as TRIPS (Trade Related aspects of Intellectual Property rightS) imposed certain minimum standards in patent protection on all member countries. This required changes in U.S. law relating in particular to the minimum duration of a patent and to prevent discrimination between the protection of inventions made in the United States and those made elsewhere. Further changes made in 1999, also had international norms as a guide and were at least in part the result of a bilateral agreement with Japan in which both countries agreed to remove some of the features of their patent system that the other found objectionable.
Some of the major changes that have been made since 1952 are as follows:
- 1954 Provisions relating to plant patents were amended to make it clear that cultivated sports, mutants, hybrids and newly found seedlings were patentable.
- 1964 Commissioner given the power to accept a declaration in lieu of an oath in "any document" and to give provisional acceptance to a defective document. 35 USC 25 and 26.
- 1965 Presumption of validity applied independently to each claim of a patent 35 USC 282.
- 1966 Supreme Court decision in Graham v. John Deere set out the proper test for deciding whether or not a claimed invention is obvious.
- 1968 Patent Cooperation Treaty signed.
- 1971 Supreme Court decision in Blonder-Tongue v. University of Illinois  held that once a patent had finally been held to be invalid after full and fair litigation, that finding could be used as a defense in subsequent litigation on that patent even if the parties differed.
- 1. Name of "The Patent Office" changed to "The Patent and Trademark Office".
2. Amendments to accommodate the Patent Cooperation Treaty. 35 USC 102(e), 104, 351- 376.
3. Liberalized the law having regard to the writing of claims in multiply dependent form. 35 USC 112.
- 1. European Patent Office opened.
2. Patent Cooperation Treaty came into effect.
- 1. Requirement to pay maintenance fees to keep patent in force introduced. 35 USC 154.
2. Special provisions made for inventions made with Federal assistance. 35 USC 200 - 211.
3. Provision made for third parties to cite prior art to USPTO. 35 USC 301.
4. Possibility of requesting reexamination created. 25 USC 302-7.
5. United States rebuffs attempts by developing countries to amend Paris Convention to permit exclusive compulsory licensing.
6. Supreme Court upholds the patentability of a genetically modified bacterium quoting the Congressional report leading up to the 1952 Act that "anything made by man under the sun" should be patentable. 
- 1. Applications permitted to be filed without signature by the inventor as long as the inventor had authorized the application to be filed. 35 USC 111
2. Law relating to correction of wrongly named inventors liberalized. 35 USC 116.
3. Court of Appeals for the Federal Circuit created. 35 USC 141, 28 USC 1295. 
4. Term of all design patents fixed at fourteen years from grant. 35 USC 173.
5. Arbitration of disputes relating to patent infringement or validity authorized 35 USC 294.
6. It became possible for United States applicants to request an international search under the PCT by the European Patent Office.
- 1. Possibility of extending patent term to compensate for delay in securing marketing authority from FDA to sell new drugs for humans. (Waxman Hatch Amendments)  35 USC 156
2. Protection from finding of obviousness over work of co-employees etc. 35 USC 103 (c).
3. Clarification that to be a joint inventor the inventors did not have to work together or each be an inventor of subject matter of every claim. 35 USC 115(a).
4. Settlement of interferences by arbitration became permissible. 35 USC 135(d).
5. Definition of infringement amended to include exports of kits of parts that can be used to make a product which if made in the U.S. would be an infringement of a U.S. Patent.  35 USC 271(f)
6. Boards of Patent Appeals and Interferences consolidated into a single Board of Patent Appeals and Interferences. 35 USC 141.
7. Statutory Invention Registration scheme introduced 35 USC 157.
8. United States succeeds in causing inclusion of intellectual property issues in Uruguay Round of GATT negotiations.
- 1. United States implements Chapter II of PCT. 35 USC 362.
2. It became possible for United States' applicants to request an international preliminary examination under the PCT by the European Patent Office.
- 1. Possibility of extending patent term to compensate for delay in securing marketing authority from FDA to sell new drugs for animals. 35 USC 156.
2. Requirements for securing permission to file patent application abroad if on file in U.S. for less than six months relaxed to some extent. 35 USC 184 and 185.
3. Definition of infringement amended to include importation into the United States of products made abroad by a process covered by a U.S. patent and to reverse the burden of proof in certain cases of alleged infringement of a process patent. (Process Patents Amendment Act) 35 USC 271(g), 35 USC 287, 35 USC 295.
4. Definition of infringement amended to include application to FDA for marketing approval of a patented drug to be effective before the expiration of the patent but to remove from patent infringement acts relating to collecting data for use in submissions to the FDA for marketing approval of a drug etc. 35 USC 271(e).
5. Patent Misuse Reform Act made it clear that patent was not unenforceable for misuse on the basis that patentee had refused to license the patent or on the basis of tying arrangements unless the patentee had market power in the relevant market. 35 USC 271(d).
- 1990 Extension of definition of patent infringement to acts in outer space on a "space object or component thereof under the jurisdiction or control of the United States". 35 USC 105
- 1992 State governments made liable for acts of patent infringement. 35 USC 271(h), 35 USC 296
- 1993 Extension of right to prove prior invention to acts carried out in NAFTA countries (35 USC 104)
- 1. Uruguay Round of negotiations for revision of the General Agreement of Tariffs and Trade (GATT), concludes an agreement on Trade Related Aspects of Intellectual Property Rights (TRIPS) which include enforceable minimum standards for patent protection.
2. Extension of right to prove prior invention to acts carried out in WTO countries (35 USC 104)
3. Introduced the possibility of filing provisional patent applications. 35 USC 111(b) and 119(e)
4. Subject to transitional provisions, the term of a patent is now twenty tears from its earliest filing date (instead of seventeen years from grant), subject to the possibility of extension to compensate for delays due to interferences or the need to appeal in order to secure the grant of the patent. 35 USC 154
5. Definition of infringing acts extended to include offers for sale and acts of importation. 35 USC 271
6. Reversal of burden of proof in certain cases where infringement of process patent is alleged. 35 USC 295
- 1995 Protection of biotechnology processes from finding of obviousness if it is for the production of new and nonobvious product. (35 USC 103 (b))
- 1996 Removal of remedies for infringement of patents for surgical processes. (35 USC 287(c).
- 1998 The Court of Appeals for the Federal Circuit in State Street Bank v. Signature Financial. holds that there is no prohibition in U.S. law on patents for business methods as long as they are new, useful and non-obvious.
- 1. The 1992 amendment to make state governments liable for act of patent infringement is held to be an unconstitutional abridgement of the states' sovereign immunity in Florida Prepaid Postsecodary Education Expense Board v. College Savings Bank. 
2. The Intellectual Property and Communications Omnibus Reform Act of 1999 is passed. This law makes a number of amendments to the United States Patent Law and also includes provisions intended to curtail cybersquatting and to deal with satellite home viewing and rural local television signals. The changes to the United States Patent Law include providing for early publication of patent applications where equivalent applications are published abroad, the protection of inventors using the services of invention promotion services and first inventor (prior user) defense for prior users of business methods. Other changes were also made to the US Patent Law. You can learn more by referring to the following articles: US Patent Law Amendments 1999 and United States - 1999 - 2000 Revisions of the Patent Law and Rules.
- 2001 The first publication of a pending United States Patent Application, as provided for by the 1999 amendment, occurs on March 15, 2001.
- 2002 Amendments relating to re-examination practice to try to make this option more useful and to clarify the law on the effect of a third party’s prior PCT application on a later-filed U.S. application.
- 2003 Amendment to the Hatch-Waxman Amendments to try to rectify some problems that had emerged.
- 2004 Cooperative Research and Technology Enhancement Act  removes prior unpublished work by joint venture partners from scope of prior art to be considered in obviousness determinations.
- 2005 Legislation introduced proposing major reforms, including a switch to a first-to-file system. (Not enacted due to lack of agrement on how to calculate damages).
- 2006 Supreme Court holds that since the grant of an injunction against patent infringement is an equitable remedy, the traditional requirements of equity must be complied with if an injunction is to be granted. 
1. The Supreme Court reviews the standards to be used in assessing obviousness in KSR v. Teleflex.
2. Introduction of non-traditional examination routes such as patent prosecution highways and peer to patent reviews to try to expedite and improve quality of patent examination.
3. Further attempt at patent law reform legislation (not enacted).
- 2009 Patent law reform legislation introduced to Congress based on compromise to deal with the issues that had thwarted reform in two previous Congresses.