Disunion follows the Civil War as it unfolded.

We’ve grown used to seeing our lives mapped. The 2010 Census has provided material for a host of new maps that profile Americans in myriad ways, from population dynamics to social and economic patterns. But the role of maps in visualizing United States Census results is actually a practice that originated 150 years ago, in the crisis between North and South.

An earlier post in this series described the efforts of the Coast Survey to map the distribution of slavery across the South in the summer of 1861. At about the same time, another pathbreaking effort was underway to “measure” the productivity of Southern slavery. The map is not well known, but its creator was none other than Frederick Law Olmsted, the designer of New York’s Central Park and one of the pioneers of American landscape architecture.

Olmsted was already an accomplished journalist when he met Henry Raymond, the editor of the newly established New-York Daily Times (later The New York Times) in the early 1850s. After just five minutes of conversation, Raymond was so impressed that he made Olmsted a special correspondent, and sent him to observe and write about Southern life. For the next several years Olmsted sent back voluminous reports — published in three volumes — of disorder, poverty, inefficiency, backwardness and chaos. We might dismiss these as hopelessly biased Northern observations, yet these accounts gained a wide audience, and challenged the contemporary picture of the cotton south as an economic powerhouse.

The Norman B. Leventhal Map Center at the Boston Public Library.

With the onset of secession, Olmsted decided to reissue his observations in a single publication. He was motivated by the possibility that the British might formally recognize the Confederacy, or — worse yet — directly intervene in the crisis. To help him edit the manuscript Olmsted hired Daniel Goodloe, a well-known abolitionist and editor who had written his own extensive critiques of slavery. Finding the returns of the 1860 Census insufficiently organized, they relied on the 1850 Census to make their case.

Olmsted and Goodloe identified slave labor as the single most damaging influence on the southern economy: it was inefficient, absorbed capital away from reinvestment, and required substantial overhead. Worst of all, the price of slaves drove cotton production — rather than the other way around — and was immune to competition from free labor. Such a system could never generate real prosperity. Even Olmsted’s title, “The Cotton Kingdom,” turned the South Carolina politician James Henry Hammond’s famous phrase — “Cotton is King” — on its head. Instead of a place of wealth and economic superiority, Olmsted found a closed society imprisoned by the crop, unable to advance, diversify or feed its own people. This was entirely an economic — rather than a moral or humanitarian — case against slavery, for the authors were tailoring their case for a British public concerned about their cotton supply.

As the secession crisis worsened in the spring of 1861, Goodloe and Olmsted raced to complete the project. On May 13 the Queen declared a policy of neutrality, which amounted to a recognition of the rebellion (though not an acknowledgement of its sovereignty). This diplomatic crisis probably motivated Goodloe and Olmsted to map the productivity of cotton. Olmsted made his case against slavery in 800 pages of narrative detail, but the map conveyed the same message in a single image: slavery was not worth defending.

Related Disunion Highlights Explore multimedia from the series and navigate through past posts, as well as photos and articles from the Times archive. See the Highlights »

Like the Coast Survey’s map of slavery in the Southern states, the map used Census data to illuminate Southern strengths and resources. Olmsted and Goodloe identified two variables on the map: the relationship of the free and slave population and the production of cotton. They separated areas where slaves outnumbered freemen, and the reverse. Then they classed regions according to high, medium and low output, shrewdly leaving readers to conclude just how inefficient slave labor really was. In most cases, the areas of high production had relatively low slave populations. Those areas shaded as highly productive but without corresponding slave populations were, in their view, direct evidence against slavery.

By June, Olmsted’s manuscript was on its way to England, where it was rushed to print by October (the American edition appeared the following month). It was heavily discussed in the British press, and sold well enough to prompt a reprint in 1862. Olmsted and Goodloe weren’t the first to say that slavery was a doomed system, but they were the first to use cartography to make their case, first to the British, and then to their fellow Americans.

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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.” She is writing a book about the rise of thematic mapping in the United States.