Disunion follows the Civil War as it unfolded.

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.

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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.

Instead, the emphasis is on parish boundaries, within which are listed free and slave populations alongside data about resources, from swine to ginned cotton. While this population data would have been available as early as 1862, the agricultural data was only published in 1864. With this information, officers and administrators moving through the state could locate the richest parishes, the largest sources of labor and the easiest means of river and rail transportation. (Oddly, the map does not list the output from over 1,500 sugar plantations located along the lower Mississippi River.)

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The Census Office was experimenting with this type of map throughout the war. At the request of Gen. William Tecumseh Sherman, for instance, the superintendent of the census annotated a previously printed map of Georgia with information on livestock and crop yields as the former embarked on his ambitious march in the fall of 1864 deep into enemy territory. But Louisiana presented an entirely different — though equally unprecedented — challenge to the Union Army: how to control and administer a conquered region where nearly half the population was no longer strictly enslaved, but which was largely exempt from the Emancipation Proclamation.

The quandary began in April 1862, when Adm. David Farragut captured New Orleans. Soon after, President Lincoln appointed Gen. Benjamin Butler as commander of the gulf. Lincoln hoped to cultivate Unionist sentiment in New Orleans, and thereby lure Louisiana out of the Confederacy. But Butler’s rigid policies and questionable confiscation of cotton alienated many in New Orleans and the parishes beyond, even though his military quarantine effectively ended the murderous yellow fever epidemic that had ravaged the city for decades.

Butler’s tenure was brief, and by the end of 1862 Lincoln had replaced him with the former governor of Massachusetts, Maj. Gen. Nathaniel P. Banks. As commander of the gulf, Banks’s military charge was to expand the realm of Union control into Texas and up the Mississippi. But equally complex was the political task of governing an area under Union occupation. In 1860 Louisiana had a population of 600,000, slightly more than half of whom were white. Yet in some of the parishes with large plantations, blacks far outnumbered whites, especially after the war took men of military age to the Confederate Army. The Confiscation Act of March 1862 prohibited Union soldiers from returning slaves to their masters, and thereby the very presence of the Army disrupted slavery. But without any clear mandate for emancipation, many of the conditions of slavery remained. Louisiana was in limbo.

Thus Banks faced the problem of rebuilding an immensely fertile region with a profoundly unstable (and still unfree) labor system. That’s where the map came in, for it allowed Banks to see the general economic capacity of the state. While such data would have been available to anyone with access to the published records of the 1860 census (published in 1862), to see such information organized geographically enabled Banks to think strategically about managing the population, its chief crop and its food supply.

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Banks’s system of labor contracts drew intense criticism from all sides, including freedmen, former plantation owners and especially antislavery Republicans in the Union. Historians have also judged it harshly for its repressive techniques, which reflected a desire to control the black population and keep plantations functioning. At the height of its operation in 1864, Banks’s system of labor contracts involved 50,000 laborers on 1,500 estates. And in part because of his labor policies, the state’s agricultural production grew significantly in 1863. In this situation, Banks probably used the map to measure the strength and resources of individual parishes. The map probably also aided Banks as he began to conscript blacks (sometimes forcibly) into the Army. By the end of 1864 he had organized more than 28 regiments, which meant that Louisiana contributed more black soldiers to the Union Army than any other state.

In these various ways, the map measured the population and its resources. In this respect the map anticipates the extensive Federal mapping efforts of the Census after the war; by the 20th century, such cartographic and statistical tools of governance had become routine.

In both the management of labor and soldiers, the map enabled Banks to govern and control by seeing the aggregate strength and composition of the population and its resources. In this respect the map anticipated the extensive federal mapping efforts of the census in postwar decades; today we live with such tools as a matter of course.

In the summer of 1864, Louisiana designed a new state constitution that abolished slavery. Thereafter, in some respects, the map was immediately outdated, and in fact it may be one of the last maps that used the term “slave.” Yet while such a category was crumbling throughout 1864, the conditions of true freedom lay far in the future, and in fact Banks’ strict efforts to regulate the movement of African-Americans laid the groundwork for the punitive black codes of the early Reconstruction period. After all, his primary goal was to control the population, and in this respect the map was no mystery at all, but the result of the logic of war.

Map courtesy of the National Archives and Records Administration in College Park, Maryland.



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Susan Schulten is a history professor at the University of Denver and the author of “The Geographical Imagination in America, 1880-1950” and “Mapping the Nation: History and Cartography in Nineteenth-Century America.”