The National Archives & Records Administration (NARA), or Archives.gov, is the major archives website for government information—interpreted broadly so as to include material such as military and older Census records.
Note: some of the following reference guides were published some time ago. They are still valuable resources for older collections of archives but be aware that they will not refer to newer material or to newer methods of access. Also, NARA publications dated prior to 1986 are classified GS 4.; after that date, AE 2.
The Library has other publications from the National Archives of interest to researchers, especially items in these series:
The Library of Congress Digital Collections portal provides access to organized collections of digitized material from the agency and other institutions.
The variety of materials available is astounding: papers and official documents from political figures, Indian tribal music, maps, various collections of pamphlets, many collections of films, photographs, and audio files, manuscripts from authors and poets, and much more.