Since the turn of the 19th century, development of large cotton plantations had taken place across the upland Black Belt after the invention of the cotton gin made short-staple cotton profitable. Cotton had added dramatically to the state's wealth. The owners' wealth depended on the labor of hundreds of thousands of enslaved African Americans, many initially transported in the domestic trade from the Upper South, which resulted in one million workers being relocated to the South. In other parts of the state, the soil supported only subsistence farming. Most of the yeoman farmers owned few or no slaves. By 1860 the investment and profits in cotton production resulted in planters holding 435,000 enslaved African Americans, who made up 45% of the state's population.