The first United States census, conducted in 1790, reported a population of 3,929,214.
Congress authorized the census under Article I of the Constitution, which required an enumeration for apportioning seats in the House of Representatives. Marshals of the federal judicial districts collected the information, beginning in August 1790 and continuing in some areas into 1791.
The count covered the original thirteen states, plus the districts of Kentucky, Maine, and Vermont. It recorded free people and enslaved people separately and excluded most Native Americans living outside taxable communities under the census rules of the time.
The total was lower than some earlier estimates, leading to debate about undercounting and incomplete returns. Even so, the census established the recurring constitutional practice of measuring the population every ten years.