Interregional slave trade

The interregional slave trade, also known as the Second Middle Passage, was the trade of slaves within the United States that reallocated slaves across states during the antebellum period. The direction of this trade occurred primarily from states of the Old South (Georgia, Maryland, Delaware, Virginia, Tennessee, Kentucky, South Carolina, North Carolina, and the District of Columbia) to states of the Deep South and the West Territories (Texas, Louisiana, Mississippi, Alabama, Arkansas, Florida). Transactions in the interregional slave market were driven primarily by interregional differences in the marginal productivity of labor, which were given by the relative advantage between climates for the production of staple goods. This disparity in productivity created arbitrage opportunities for traders to exploit and ultimately facilitated regional specialization in labor production. Due to a lack of data, particularly with regard to slave prices, land values, and export totals for slaves, the true effects of the interregional slave trade on both the economy of the Old South and general migration patterns of slaves into southwestward territories remain uncertain and have served as points of contention among economic historians.

The internal slave trade among states emerged in 1760 as a source of labor in early America. Along with other factors, the abolition of transatlantic slave trade in 1809 placed increased importance on the role of this interregional trade. It is estimated that between 1790 and 1860 approximately 835,000 slaves were imported to the American South. However, analysis by Robert Fogel and Stanley Engelman suggests that only 16 percent of the total migration of slaves was due to sale of slaves through domestic trade.

The biggest sources for the domestic slave trade came from exporting states in the Upper South such as Virginia, North Carolina, Maryland, and Kentucky. From these states most slaves were imported into South Carolina, Georgia, Alabama, Mississippi, Louisiana, and Arkansas. Fogel and Engelman attribute the larger proportion of interregional slave migration (i.e. migration not due to slave trade) to movement as whole plantations with slave owners.

Historians who argue in favor of soil exhaustion as an explanation for slave importation into the Deep South posit that exporting states emerged as slave producers because of the transformation of agriculture in the upper south and the increased demand for labor in the Deep South due to the success of sugar and cotton crops. Because of the deterioration of soil and an increase in demand for food products, states in the upper south shifted crop emphasis from tobacco to grain which required less slave labor. This decreased demand left states in the Upper South with an excess supply of labor.

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