The Fifteenth Census Act, approved June 18, 1929, authorized "a census of population, agriculture, irrigation, drainage, distribution, unemployment, and mines [to be] taken by the Director of the Census." This act was the first to specify only general areas to be investigated, leaving the content of specific questions to the discretion of the director. The census encompassed each state, along with Washington, DC, Alaska, Hawaii, and Puerto Rico. The governors of Guam, American Samoa, and the Virgin Islands each completed a census that same year. So did the governor of the Panama Canal Zone.

In the time between the passage of the act and census day, the stock market crashed and the nation plunged into the Great Depression. The public and academics wanted quick access to the unemployment information collected in the 1930 census. The Census Bureau had not planned to process the unemployment information it had collected - which some statisticians considered unreliable - until quite a bit later and was unequipped to meet these demands. When it did rush its data on unemployment out, the numbers it reported were attacked as being too low. Congress required a special unemployment census for January 1931; the data it produced confirmed the severity of the situation.

Congress mandated that another unemployment census be conducted in 1937. This special census was largely voluntary; postal carriers delivered a form to every residential address in the country and those who were unemployed were expected to fill it out and mail it back. This special census is noteworthy because it was an early opportunity for Census Bureau statisticians to experiment with statistical sampling. Two percent of households were delivered a special census questionnaire whose results were used to test the accuracy of the larger census.