Black Belt, term applied to several areas of Mississippi and Alabama, the heart of the Old South, which are characterized by black soil and excellent cotton-growing conditions. The Black Belt area was historically important as the nation's main cotton producer in the mid-1800s. Soil depletion, erosion, the boll weevil, and economic conditions combined to eliminate cotton from the region. Livestock, peanuts, and soybeans have become the area's chief crops.