On what date was the first U.S. census taken?

The first U.S. census was taken on August 2, 1790. This date, called Census Day, established the population reference point for the nation’s first federal population count.

Article I, Section 2 of the Constitution required an enumeration of the population for congressional representation and direct taxation. Congress passed legislation assigning the work to U.S. marshals in the federal judicial districts, who visited households and compiled returns.

The census recorded people in categories that included free white males, free white females, other free persons, and enslaved people. It counted roughly 3.9 million inhabitants, although historical totals were later corrected as additional information was found. Virginia was the most populous state, with 747,610 people in the original enumeration.

The results were published in 1791 in a 56-page report. Secretary of State Thomas Jefferson and President George Washington both suspected that the census had undercounted the population because of the country’s large area, limited transportation, and difficulties reaching every household. Modern censuses continue to use a designated reference date, even though collection may take longer.