U.S. Patent law is found in Title 35 of the United States Code, which is one of the titles that has been enacted into positive law by Congress - meaning that Title 35 is legal evidence of the law in all U.S. courts.
The United States Code can be found online at the website of its publisher, the Office of the Law Revision Counsel of the United States House of Representatives
The U.S. Code is also available online at GovInfo.
Annotated versions of the United States Code are published by West (United States Code Annotated or U.S.C.A.) and Lexis (United States Code Service or U.S.C.S.) and are available online in both services. HeinOnline offers full historic coverage of the print edition of the U.S. Code, which can be useful when faced with an issue based on a previous copyright law.
Patent Act of 1952
Patent and Trademark Law Amendments Act (Bayh–Dole Act)
Drug Price Competition and Patent Term Restoration Act of 1984
Patent Law Amendments Act of 1984
American Inventors Protection Act of 1999
PRO-IP Act
Leahy-Smith America Invents Act