From the Wikipedia page 
The Federal Depository Library Program (FDLP) is a government program created to make U.S. federal government publications available to the public at no cost. As of June 2008, there were 1,252 depository libraries in the United States and its territories. A "government publication" is defined in the U.S. Code as "informational matter which is published as an individual document at Government expense, or as required by law" (44 U.S.C. 1901).
The website is here