Ohio's physical geography is defined by two major water systems: Lake Erie to the north and the Ohio River to the south. The state acts as a transition zone between the flat expanses of the Midwestern plains and the rugged terrain of the Appalachian Mountains.
Geographically, Ohio is divided into a few primary regions. The Great Lakes Plains run along the northern border, characterized by fertile, relatively flat land that once included the massive Great Black Swamp. The Till Plains cover the western and central parts of the state, featuring rolling hills and exceptionally rich soil deposited by ancient glaciers. To the east and southeast lies the unglaciated Allegheny Plateau, a rugged, forested area characterized by steep valleys and sandstone bedrock.
Natural resources have profoundly shaped Ohio's economy. The state contains significant deposits of coal, natural gas, and salt, particularly in the eastern Appalachian region, as well as vast tracts of productive agricultural soil. The state features diverse temperate forests consisting of oak, hickory, and beech-maple ecosystems.