Complex sentence: The Quapaw had inhabited lands along the Arkansas River and near the Arkansas River's mouth at the Mississippi River for centuries but the Industrial Revolution had increased demand for cotton, a crop that grew well in fertile delta soils.
Split into simpler sentences: The Quapaw had inhabited lands along the Arkansas River and near its mouth at the Mississippi River for centuries. The Industrial Revolution had increased demand for cotton, a crop that grew well in fertile delta soils.