The website of the United States Census Bureau contains extensive archives. All census information after 1940 is available on the site; earlier records are maintained by the National Archives and Records Administration.
The publication, Statistical Abstract of the United States, gives detailed information and statistics on the social, political and economic organization of the United States, including population figures. The abstract was published from 1878 to 2012 and includes the report from 1977. It is available for download in PDF format and consists of 13 parts, although it can be downloaded as a single document. The site also offers data from the American Housing Survey, which was sponsored by the U.S. Department of Housing and Urban Development and conducted by the U.S. Census Bureau. These documents may also be downloaded.