The first U.S. census, conducted in 1790, recorded a population of 3,929,214 people.
The census was authorized by the Constitution and carried out under the Census Act of 1790. Marshals visited households and recorded free people, enslaved people, and other population categories according to the legal classifications of the era. The enumeration covered the original 13 states, plus the districts of Kentucky, Maine, and Vermont, and the Southwest Territory.
Secretary of State Thomas Jefferson received the final totals, which were reported in 1791. The count was used to allocate seats in the House of Representatives and helped establish the constitutional practice of taking a census every ten years.
The figure is a historical count, not a modern estimate of everyone living within today's United States. The country had different boundaries, and the census's categories excluded or handled some groups differently from modern censuses. The 1790 total also reflected slavery, which accounted for roughly one-fifth of the recorded population.