The United States Patent and Trademark Office features a variety of online searching tools that allow anyone to search through patent information without cost. The full-text patent search tool contains patents dating back to 1976, while the image patent search goes back to 1790.
The online full-text patent search has quick search and advanced search option, both of which allow anyone to search patents based on key terms within the actual patent application. The quick search feature allows for up to two terms to be searched from up to fields, such as applicant state, inventor name and issue date. The advanced search allows for more complex queries into the database based on numerous fields in conjunction.
The image patent search goes back to 1790, but does not offer any complex or comprehensive search capability. The online information available for the patents in this date range consists of PDF scans of the actual patent applications and forms. As such, the only way to search this information is with the specific patent number.
The United States Patent and Trademark Office headquarters in Alexandria, Virginia, has a Patent and Trademark Resource Center that allows anyone who visits to search through all available patents and view them in a variety of formats.