After 72 years of privacy protection lapses, intimate details of 132 million people who lived through the 1930s will be disclosed as the US government releases the 1940 census on April 2 to the public for the first time. Access to the records will be free and open to anyone on the Internet, though finding a name among the 3.8 million digitized images won't be a snap: It could be at least six months after the release before a nationwide name index is created.
In the meantime, researchers will need an address to determine a census enumeration district—a way to carve up the map for surveying—to identify where someone lived and then browse the records. But for genealogists and family historians, the 1940 census release is the most important disclosure of ancestral secrets in a decade and could shake the branches of many family trees. Researchers might be able to follow the movement of refugees from war-torn Europe in the latter half of the 1930s; sketch out in more detail where 100,000 Japanese Americans interned during World War II were living before they were removed; and more fully trace the decades-long migration of blacks from the rural South to cities. (Read more Great Depression stories.)