These days the intersection of cartography and Big Data is all the rage: Using information from the 2010 census, countless news outfits, including The New York Times, have created tools allowing readers to make customized maps of everything from trends in ethnic and racial composition to the dynamics of housing development. Indeed, we have come to expect that any large body of data will be visualized through maps and infographics. Such tools help to transform information into knowledge, and at their best allow us to see patterns that might otherwise be lost.
But while the technology may be new, the idea of mapping data in the United States can actually be traced to the Civil War. Earlier posts in Disunion have discussed the maps of slavery generated by the United States Coast Survey. At the same time, the Census Office (also part of the Treasury Department) was experimenting with maps of not just one but multiple types of data. These were designed to aid the Union war effort, but perhaps more importantly to plan for Reconstruction.
One of the most fascinating — and mysterious — of these experiments is an unsigned, undated map of Louisiana, buried within the voluminous war records of the National Archives. The map contains almost no environmental information save for the river systems and a few railroads. Even roads are omitted, truly unusual for any 19th-century map.