When the U.S. Census Bureau conducted the 1940 census, America was on the brink of a war that would change the nation forever. The country was emerging from the trials of the Great Depression, but as hope returned a new menace was on the horizon. Americans were reluctant to become involved in conflicts overseas, believing that it was more important to focus on rebuilding the country in the wake of the devastating stock market crash, but history had a different path in mind. Although peace was not immediately in the cards, the 1940s saw an explosion in technology, financial prosperity, and world leadership for the United States.

The 1940 U.S. census has been kept secret for 72 years, but now the records of that momentous time in the nation’s history have been released. The National Archives in Washington have made the records public, making this the first time individual records from a census are available online in a fully digitized form, with free access to anyone. Just a decade ago, census records came as microfilm and a genealogical search for family history meant an arduous hunt through spools of film at the nearest participating library. The release of the 1940 census data marks a new, golden era for genealogical research.

The Census count of the population is conducted every 10 years, as ordered by the Constitution. Some of the information is rapidly made public, like population numbers by sex, age, and ethnic or racial background, as well as other data regarding family structure, housing, income, and education.

Other, more sensitive information (like names and addresses, and the answers to questions about education level, employment, wages, and the value of home or cost of rent) that could reveal personal data about the individuals is kept confidential. To protect privacy, a federal law was enacted in 1978 to restrict personal information about a person collected in the decennial census to anyone but that particular individual (or heirs) for 72 years.

Searches  of the 1940 census cannot yet be done by name – only by the enumeration district in which someone lived or the area each of the 120,000 census-takers was assigned to comb – but that hasn’t stopped a flood of genealogists from accessing the newly-available records. The National Archives reported that the site received 37 million hits hours after the records went public, a storm of unprecedented interest that nearly brought the site down.

For more information on a service that allows you to use this type of information to find your family history, you can read our Ancestry review.