The first US census day was 8/2/1790 and determined that the US population was 3,893,635. The Census included the 13 original states, plus the districts of Kentucky, Maine, Vermont and the Southwest Territory (TN). It included free White males, free White females, all other free persons, and all slaves. Washington was skeptical of the final tally; he expected a number over 3.9 million. Happy Census Day; fill out your form!