1940 United States census
The 1940 United States census, conducted by the Census Bureau, determined the resident population of the United States to be 132,164,569, an increase of 7.6 percent over the 1930 population of 122,775,046 people. The census date of record was April 1, 1940.
A number of new questions were asked including where people were five years before, highest educational grade achieved, and information about wages. This census introduced sampling techniques; one in 20 people were asked additional questions on the census form. Other innovations included a field test of the census in 1939. This was the first census in which every state (48) had a population greater than 100,000.
Use for Japanese American internment[edit]
During World War II, the Census Bureau responded to numerous information requests from US government agencies, including the US Army and the US Secret Service, to facilitate the internment of Japanese Americans. In his report of the operation, U.S. Army Lt. Gen. John L. DeWitt wrote that "The most important single source of information prior to the evacuation was the 1940 Census of Population."[11][12][13]