How America Has Changed Since the First Census in 1790

1940: First use of probability sampling

• U.S. resident population: 132,164,569
• Number of official states: 48
• Median age of population: 30.2
• Immigrants obtaining legal resident status: 70,756
• Biggest cities: New York, NY (Population: 7,454,995), Chicago, IL (3,396,808), Philadelphia, PA (1,931,334)

The 1940 Census was the first national census to utilize probability sampling, a statistical technique in which subjects are randomly selected in order to ensure that a small sample accurately reflects an entire population.

This technique allowed the number of questions asked by the Census Bureau to be raised without putting a huge strain on the respondents or on the analysts who would process the data and allowed census results to be released much earlier. New questions this year discussed employment, unemployment, internal migration, and income.