MONONGAHELA, a river of the United States of North America, rises in Randolph county, Virginia, in terlocking with the sources of the Great Kenhawa at N. Lat. 38° 30'. Its course is nearly south 80 miles, to where it receives the west branch, from Lewis and Ilar risen counties. Below their junction, the united stream flows south-east 30 miles to the south boundary of Pennsylvania, which it passes, and two miles lower receives from the south-east, Cheat river, little, if any, inferior in column or length to the Monongahela itself. Cheat river rises in Randolph county, and flows through that and Monongahela county, enters Pennsylvania, and unites with the main stream as hcfore noticed. The sources of the Monongahela and Cheat are in the west ern spurs of the Appalachian mountains. Below the mouth of Cheat, the Monongahela flows nearly south 50 miles, to its junction with the Youghiogheny. The latter rises in the Appalachian mountains, in Allegheny county, in Maryland, interlocking with the sources of the North Branch of the Potomac, flows north into Pennsylvania, passing through Fayette, IVestmoreland,and entering Al legheny county,unites with the Monongahela at po•t, after a comparative course of about 100 miles.
Twelve miles below its junction with Youghiogheny, the Monongahela unites with the Allegheny, and forms the Ohio at the city of Pittsburg. The entire length of the Monongahela river, by comparative courses, is about 170 miles, but following the meanders of the streams, either along the main or Cheat branch, the length ex ceeds 200 miles.
The country drained by the Monongahela is in some parts mountainous, and in all hilly.
For down stream navigation, the Monongahela, at high water, is passable with large boats as high as the mouth of the West Branch, and by lighter vessels much higher. Cheat river is navigable into Randolph county, about 50 miles comparative course above its mouth, and the Youghiogheny to the Ohiopyle falls, in Fayette county, 60 miles above its junction with the Monon abela. (DAnnv.)