Lincoln Mullen, The Spread of U.S Slavery, 1790 - 1860

This interactive map, created by historian Lincoln Mullen using U.S. Census data, depicts the spread of slavery from 1790 to 1860. As Mullen thoroughly explains here, the map allows users to adjust the variable depicted on the map, including the population of slaves, free African Americans, all free people, or the entire United States; all subjects as population densities; or all subjects as percentages of the population. Users can also use the date range slider at the bottom of the map to see change over time for any given variable. According to Mullen, the map highlights that the population of enslaved people spread more than it grew, mostly expanding into the fertile lands of Georgia, Alabama, Mississippi and most of the Mississippi River Valley, and that a strikingly high percentage of the population in the South was enslaved, demonstrating the importance of slavery to the Southern economy. The map is a valuable resource to use in combination with Hergesheimer's 1861 Map Showing the Distribution of the Slave Population of the Southern States of the United States, also highlighted on this website.