In this photo provided by the National Archives at College Park, an enumerator interviews a woman for the 1940 Census. Veiled in secrecy for 72 years because of privacy protections, the 1940 U.S. Census is the first historical federal decennial survey to be made available on the Internet initially rather than on microfilm. (AP Photo/National Archives at College Park)
The 1940 census records were released Apr. 2, with more than 21 million people alive in the U.S. and Puerto Rico.