The Spread of Slavery in the United States

In September, 1861 the U.S. Coast Survey published this large map showing the enslaved population by county. It was "sold for the benefit of the sick and wounded soldiers of the U.S. Army."

The image above is from an article in Smithsonian. Here is a detailed view showing part of the Carolinas with the county names and enslaved populations.

The articles' author, Lincoln Mullen created a series of animations.

On his own page are some interactive maps where you can choose variables such as free African Americans and total population and choose your year from a slider at the bottom. This allows you to see the high slavery numbers in 1790 in places like eastern New York and Northern New Jersey.

Or see where free African Americans were clustered in different years.

Here is one showing all free persons by percentage from 1810.

You can explore on your own here and read more about the westward expansion of slavery here.