The Ohio River is a mile-long 1, km river in the United States. It is located at the boundary of the Midwestern and Southern United States , flowing in a southwesterly direction from western Pennsylvania to its mouth on the Mississippi River at the southern tip of Illinois. It is the third largest river by discharge volume in the United States and the largest tributary by volume of the north-south flowing Mississippi River, which divides the eastern from western United States.
The river flows through or along the border of six states , and its drainage basin includes parts of 14 states. Through its largest tributary, the Tennessee River , the basin includes several states of the southeastern U. It is the source of drinking water for five million people.
The river became a primary transportation route for pioneers during the westward expansion of the early U. The lower Ohio River just below Louisville was obstructed by rapids known as the Falls of the Ohio where the elevation falls 26 feet 7. Since the "canalization" of the river in , the Ohio has not been a natural free-flowing river; today, it is divided into 21 discrete pools or reservoirs by 20 locks and dams for navigation and power generation.
The name "Ohio" comes from the Seneca , Ohi:yo' , lit. Its current gentle, waters clear, and bosom smooth and unbroken by rocks and rapids, a single instance only excepted. After the French and Indian War , Britain's trans-Appalachian Indian Reserve was divided by the river into colonial lands to the south and Native American lands to the north.
In the late 18th century, the river became the southern boundary of the Northwest Territory. The river is sometimes considered as the western extension of the MasonβDixon line that divided Pennsylvania from Maryland , and thus part of the border between free and slave territory, and between the Northern and Southern United States or Upper South.
