These maps reveal the expansion of slavery in America.

1861September, the US Coast Survey published a large map about two feet by three feet, entitled "Distribution Map of Slave Population in Southern States of the United States". According to the population data collected in 1860 census and certified by the director of census bureau, the map depicts the percentage of enslaved population in each county. At a glance, the audience can see a large-scale model of the economic system that has kept nearly 4 million people in slavery: slavery is concentrated in chesapeake bay and eastern Virginia; South Carolina and Georgia coasts; Crescent land in Georgia, Alabama and Mississippi; Most importantly, in the Mississippi valley. Since every county has an exact percentage of the enslaved population, this map needs to be examined more carefully.

The related content database reveals the historical connection between New York State and slavery, and the terrible fate of john castle, the first American slave on the Black Coast. Slavery map is one of many maps drawn from the data generated by the United States in the19th century. As the historian Susan Schulten showed, this special map was drawn by federal agencies based on the statistics collected by the census. Abraham lincoln has been consulting this question during the civil war. There is a banner on the map that says, "For the wounded and sick in the American army." ? Data map is a tool of * * * and a new technology representing knowledge.

Although the theme map originated in19th century, this technology is useful for us to understand history today. A basic question of history is the question of scale: how do historians move between understanding the single life of the past and the lives of millions of people, between the boundaries of cities and continents, between a period of time and centuries? Maps can't tell us everything, but they can help us, especially interactive network maps, which can be enlarged and reduced to represent more than one theme and set to show changes over time.

To help show the general model of slavery in the United States, I made an interactive map of the spread of slavery. The coastal survey map shows a measure, and the interactive map shows the population of slaves, free African Americans, all free people and the whole United States, as well as the population density and percentage of each measure to the total population. The map extends from 1790 to 1860, the first census before the civil war. You can explore the map yourself, but below I made some animations to highlight some main patterns.

When we look at all these maps together, we can notice that even during the period from 1790 to 1860, the total number of enslaved people in the United States is increasing. These slaves are scattered in the increasingly vast land of the United States, rather than concentrated in areas where slavery is well established. Atlantic States 1790 and 1800.

The slave population is approaching its peak at any time. Take Charleston County, South Carolina as an example. 1790, nearly 5 1000 people in this county were enslaved. 1840, the slave population reached a peak of nearly 59,000; By 1860, the slave population reached 37,000, only 63% of 20 years ago.

The total number of slaves in the eastern coastal States grew slowly with the passage of time, but the growth rate was different from that of free people in the north. The population of free white people in the north has increased where they settled and spread to the west.

The slave population has different dynamics. In some places around chesapeake bay, even when slavery was gradually abolished in the north, this phenomenon became more and more serious. But to a large extent, the slave population in the United States in the N century (Chicago: University of Chicago Press, 20 12) wrote a map about slavery in the fourth chapter; See also the panion website of the book, which provides pictures of slavery maps. Steven Deul wrote the latest history of the domestic slave trade in his book Take Me Back: The Domestic Slave Trade in American Life (new york: Oxford University Press, 2005). The above figures are taken from page 289. One of the many excellent slavery histories in the United States can be seen: on the settlement of the Mississippi River Basin, walter johnson, The River of Dark Dreams: Slavery and Empire in the Cotton Kingdom (Cambridge, Harvard University belknap Press, 2013); On the Life of Slaves, erskine Clark, House: An Epic of Plantation (New Haven: Yale University Press, 2005); A General History of Slavery, Ella Berlin, Generations of Prisoners: A History of Black Slavery in America (Cambridge, Massachusetts: Harvard University Press, belknap Press, 2003).

The data on my map comes from 1790 to 1860 census data collected by Minnesota Population Center (National Historical Geographic Information System) version 2.0 (Minneapolis: University of Minnesota, 201year).

U.S. Coast Survey, a map showing the distribution of slave population in southern States of the United States (Washington, D.C.: Henry S. Graham, 186 1). Pictures of the Library of Congress.