"Scarce fit for anything but Slaves and Brutes": Climate in the Old Southwest, 1798–1855

In 1798, the spanish government recruited natchez planter and natural scientist William Dunbar to survey the boundary line between the United States and Spanish Florida that ran along the 31st parallel north, which today constitutes the bulk of Alabama and Mississippi's southern border. Dunbar spent the summer trekking across the Old Southwest and recording the environmental and climatological characteristics the area. That August, camped on a bluff overlooking a floodplain from which the Mississippi River had only recently receded, Dunbar described, in vivid and horrifying detail, the effect climate had on the flora and fauna of the region. In this, the "hottest month of the year," he wrote, "the surface of the earth teems with life…not of those kinds which invite and delight the view of the inquisitive naturalist; but of the most disgusting forms and noxious kinds." He noted the nightmarish "serpents of the waters," who "frequently entwined in clusters to the number of several hundreds." He complained of the "innumerable swarms of Gnats," as well as the "variety of other Stinging and biting insects." He recounted the "hideous forms" of the "vast variety of toads, frogs…and the thundering Crocodile," as well as alluding to others, "the multitude" of which were "too numerous to mention." Dunbar considered these repulsive beasts products of the sultry environment, and he spared little ink on "extreme of heat" that preyed on him and his party. He remarked with disdain that "the thickets on either side of the avenue…were often impenetrable to the stoutest breeze." He wrote that he and his companions withered under the "ardent beams of the sun," which "might be literally said to scorch." And he recorded the temperature at a broiling 120° Fahrenheit. The accuracy of his observations proves less important than the fact that for Dunbar, the climate of the Old Southwest was uniquely and dangerously hot.¹

Confronted with what he considered a singularly unhealthy environment, Dunbar attempted to guard against the dangerous effects of high temperatures. In meeting with the American surveyor, Andrew Ellicott, at the outset of the expedition, he suggested that the teams embark in opposite directions. Ellicott and his company were to move east, towards the Atlantic Coast, while Dunbar and his team would traverse the warmer and more menacing terrain towards the Big Muddy. Dunbar explained: "the moist and Swampy Soil in the vicinity of the Mississippi being considered as hazardous to the health of our Northern friends, I proposed that the American commissioner should continue his progress eastward." Ellicott took with his party "the White laborers, 50 in number" through the less perilous territory, while Dunbar tasked himself with "pushing the line through the low grounds to the Margin of the Mississippi with the assistance of 2 surveyors, 22 black laborers and a White Overseer."²

Dunbar's allocation of labor—his decision to take with him the "22 black laborers" on the riskier western route—had everything to do what he knew about the relationship between race and heat.³ Though the belief that Africans could better tolerate high temperatures than whites had existed for centuries, the rapid peopling of the Old Southwest in the first half of the nineteenth century lent a new urgency to these considerations. As Americans flooded into the region, they cleared of millions of acres of land for cotton cultivation, increasing surface temperatures and enhancing the transmission of disease. Concurrently with their manipulation of the landscape, the global climate began to warm. At the end of the eighteenth century, the Little Ice Age—an extended period of cool temperatures and erratic weather that had started in the middle of the fourteenth-century—began to end, and temperatures rose significantly, albeit inconsistently, over the course of the nineteenth century.⁴ Expansion into a region both hotter and more prone to illness than anywhere else in the nation amplified anxieties about the physical consequences of heat in ways that prompted some scientist and physicians to reimagine the relationship between climate and race. From the time of the Louisiana Purchase...