The United States Patent and Trademark Office (USPTO) web site allows you to search for patents and published patent applications. The full-text of patents from 1976 to the present is searchable. Patents from 1790 to 1975 are searchable only by current U.S. classification number, patent number or issue date. The full-text of published patent applications since March 15, 2001 is searchable.
The USPTO advises that the most comprehensive patentability search of U.S. patents will be a search conducted by Cooperative Patent Classification (CPC) number in their patent database.
The USPTO web site also contains various tools that will help you conduct a preliminary patentability search:
As a Patent and Trademark Depository Library, the New York State Library also provides access to the USPTO's PubWEST and PubEAST search systems. These time-saving tools can help you perform a more thorough patent search and are not available on the Internet.
The New York State Library has trained staff who will assist you in learning to use these tools. Appointments are not required to use the collection but are recommended if you would like assistance in using these tools. Appointments can be made by calling 518-474-5355 or by e-mail. A directory of attorneys and agents registered to practice before the USPTO can be found on the USPTO web site.