St. Louis, Missouri, is where the Mississippi River divides into its Upper and Lower regions, marking a significant geographical point.

The city of St. Louis lies where the Upper and Lower Mississippi Rivers split. Along the river, this separation is important for ecology, climate variations, and navigation. The Lower Mississippi, going south to the Gulf of Mexico, is wider and has more commercial navigation, but the Upper Mississippi, which runs north of St. Louis, is narrower and more dam-controlled. This divide affects river management, trade, and ecology.