The cotton gin triggered a wave of monocropping that exhausted the soil across the American South.

Invented by Eli Whitney in 1793, the cotton gin automated the separation of seeds from short-staple cotton fibers. This technological shift increased productivity by 50 times compared to manual labor. Because cotton became an incredibly lucrative cash crop, plantation owners transitioned to monocropping, which is the practice of growing the same crop on the same land year after year.Cotton is a heavy feeder that requires significant amounts of nitrogen and phosphorus. Without the traditional practice of rotating crops with legumes like peas or beans, the soil's organic matter was rapidly depleted. Historical records from the 1840s show that yields in older coastal states dropped significantly as the topsoil became barren and prone to erosion.Geologists and historians refer to this period as the 'Cotton Kingdom' expansion. By 1850, the United States was producing 2.85 million bales of cotton annually, but the environmental cost was staggering. The lack of root diversity and the removal of natural vegetation led to massive gully erosion and the loss of millions of tons of fertile topsoil.This environmental degradation had profound geopolitical consequences. As the soil in the 'Old South' failed, the demand for new territory fueled the westward expansion of slavery into the Deep South and Texas. This cycle of soil exhaustion and migration was a primary driver of American economic and territorial policy throughout the 19th century.