In this photo provided by the U.S. Census Bureau, tabulators in Washington record the information from the more than 120,000 enumerators who gathered data for the 1940 U.S. 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 and Records Administration)
The 1940 census records were released Apr. 2, with more than 21 million people alive in the U.S. and Puerto Rico.