In 1800, slaves represented nearly 20 percent of the population of the United States: roughly 1 million slaves out of a total population of 5 million. In the South, where nearly all of the slaves were held,14 the proportion reached 40 percent: 1 million slaves and 1.5 million whites for a total population of 2.5 million. Not all whites owned slaves, and only a tiny minority owned as many as Jefferson: fortunes based on slavery were among the most concentrated of all.