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Interactive Map - The Spread of U.S. Slavery, 1790–1860
The Spread of U.S. Slavery, 1790–1860
Click here to access the map
If you use this map in your research, I would appreciate a citation. Here is the suggested form:
Lincoln Mullen, "The Spread of U.S. Slavery, 1790–1860," interactive map, http://lincolnmullen.com/projects/slavery/, doi: 10.5281/zenodo.9825.You should also cite the NHGIS:
Minnesota Population Center, *National Historical Geographic Information System: Version 2.0* (Minneapolis, MN: University of Minnesota, 2011), http://www.nhgis.org.
Explanation of Census data
The U.S. Census data and shapefiles for these maps comes from Minnesota Population Center, National Historical Geographic Information System, version 2.0 (Minneapolis, MN: University of Minnesota, 2011). For a description of the questions asked on the 1790 to 1860 censuses, see Measuring America: The Decennial Censuses From 1790 to 2000 (U.S Census Bureau, 2002). Bear in mind the reason the Census kept statistics on slavery. Slaves were counted in the Census because of the three-fifths compromise in the federal constitution, by which an enslaved person counted as three-fifths of a person when apportioning representation in Congress and direct taxes. I have tried to represent unavailable data on the map, but sometimes in the Census a value of zero actually means that the data has been lost or was never gathered. Treat the Census numbers skeptically: even in the best of circumstances the Census undercounts the population. For example, Harvey Amani Whitfield has shown that Vermont did have slavery, even though no slaves were enumerated in the Census. The numbers are useful chiefly for showing degrees of magnitude. Below are the fields in the NHGIS data that I have used. The total free population was always calculated by subtracting the slave population from the total population.
1790 Census
- Slave population: "Race/Slave Status: Persons: Non-White: Slave" (AAQ002)
- Total population: (A00AA1790)
- Free African American population: "Race/Slave Status: Persons: Non-White: Free" (AAQ001)
1800 Census
- Slave population: "Nonwhite Population, Except Indians Not Taxed by Slave Status: Slave" (AAY002)
- Total population: (A00AA1800)
- Free African American population: "Nonwhite Population, Except Indians Not Taxed by Slave Status: Free" (AAY001)
1810 Census
- Slave population: "Nonwhite Population, Except Indians Not Taxed by Slave Status: Slave" (AA7002)
- Total population: (A00AA1810)
- Free African American population: "Nonwhite Population, Except Indians Not Taxed by Slave Status: Free" (AA7001)
1820 Census
- Slave population: sum of "Nonwhite: slave" male and female columns for "Race/Slave Status by Sex" (ABB003 and ABB004)
- Total population: (A00AA1820)
- Free African American population: sum of "Nonwhite: free" male and female columns for "Race/Slave Status by Sex" (ABB005 and ABB006)
1830 Census
- Slave population: sum of "Nonwhite: slave" male and female columns for "Race/Slave Status by Sex" (ABO003 and ABO004)
- Total population: (A00AA1830)
- Free African American population: sum of "Nonwhite: free" male and female columns for "Race/Slave Status by Sex" (ABO005 and ABO006)
1840 Census
- Slave population: "Nonwhite: slave" column for "Race/Slave Status" (ACS003)
- Total population: (A00AA1840)
- Free African American population: "Nonwhite: free" column for "Race/Slave Status" (ACS002)
1850 Census
- Slave population: "Nonwhite: slave" column for "Race/Slave Status" (AE6003)
- Total population: (A00AA1840)
- Free African American population: "Nonwhite: free" column for "Race/Slave Status" (AE6002)
1860 Census
- Slave population: sum of "Slave" male and female columns for "Race by Sex" (AH2005 and AH2006)
- Total population: (A00AA1860)
- Free African American population: sum of "Free colored" male and female columns for "Race by Sex" (AH2003 and AH2004)
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