The 1860 United States census was the eighth census conducted in the United States starting June 1, 1860, and lasting five months. It determined the population of the United States to be 31,443,321 in 33 states and 10 organized territories. This was an increase of 35.6 percent over the 23,191,876 persons enumerated during the 1850 census. The total population included 3,953,760 slaves.

The United States census is a census that is legally mandated by the Constitution of the United States. It takes place every ten years. The first census after the American Revolution was taken in 1790 under Secretary of State Thomas Jefferson. There have been 23 federal censuses since that time. The census includes territories of the United States. The United States Census Bureau is responsible for conducting the census.