Answer:
In September of 1861, the U.S. Coast Survey published a large map, approximately two feet by three feet, titled a "Map showing the distribution of the slave population of the southern states of the United States." Based on the population statistics gathered in the 1860 Census, and certified by the superintendent of the Census Office, the map depicted the percentage of the population enslaved in each county. At a glance, the viewer could see the large-scale patterns of the economic system that kept nearly 4 million people in bondage: slavery was concentrated along the Chesapeake Bay and in eastern Virginia; along the South Carolina and Georgia coasts; in a crescent of lands in Georgia, Alabama and Mississippi; and most of all, in the Mississippi River Valley. With each county labeled with the exact percentage of people enslaved, the map demanded some closer examination.
The Coast Survey map of slavery was one of many maps drawn from data produced in 19th-century America. As historian Susan Schulten has shown, this particular map was created by a federal government agency from statistics gathered by the Census. Abraham Lincoln consulted it throughout the Civil War. A banner on the map proclaims that it was "sold for the benefit of the Sick and Wounded Soldiers of the U.S. Army." The data map was an instrument of government, as well as a new technology for representing knowledge
