NEW YORK –  It was decades ago when tens of millions of people in the U.S. experienced mass unemployment and social upheaval as the nation clawed its way out of the Great Depression and rumblings of global war were heard from abroad.

Now, intimate details of 132 million people who lived through the 1930s will be disclosed as the U.S. government releases the 1940 census on April 2 to the public for the first time after 72 years of privacy protection lapses.

Access to the records will be free and open to anyone on the Internet — but they will not be immediately name searchable....