The prohibition of the African slave-tradeafter 1807 limited the supply of slaves in the United States. #Slaveholders looked at the fertility of slave women as part of their productivity, and intermittently forced the women to have large numbers of children. The invention of the cotton gin enabled expanded cultivation in the uplands of short-staple cotton, leading to clearing lands cultivating cotton through large areas of the Deep South, especially the Black Belt. The demand for labor in the area increased sharply and an internal slave market expanded. At the same time, the Upper South had an excess supply of slaves because of a shift to mixed crops agriculture, which was less labor-intensive than tobacco. During this time period, the terms "breeding slaves", "child bearing women", "breeding period", and "too old to breed" became familiar. Planters in the Upper South states started selling slaves to the Deep South, generally through slave traders. Louisville, Kentucky, on the Ohio River was a major slave market and port for shipping slaves downriver by the Mississippi to the South. New Orleans had the largest slave market in the country and became the fourth largest city in the US by 1840 and the wealthiest, mostly because of its slave trade and associated businesses. #breedingfarm
