Rock river drains the waters from the northern part of Illinois and Wisconsin, and enters the parent stream at 41° 30' north latitude. In latitude 39° comes in the Illinois, signifying the "River of Men;" and eighteen miles below this, it unites with, and is lost in the Missouri.
Custom has fixed unalterably, the name Mississippi, to this united body of waters, that rolls its turbid waves towards the Mexican gulf; though, as has been intimated, it is but a continuation of the Missouri.
Sixty miles below St. Louis, the Kaskaskia joins it, after a devious course of 400 miles. In 37° north latitude, the Ohio pours in its tribute, called by the early French explorers, "La Belle Rivière," the beautiful river. A little below 34°, the White river enters after a course of more than 1,000 miles. Thirty miles below that, the Arkansas, bringing its tribute from the confines of Mexico, pours in its waters. Above Natchez, the Yazoo from the east, and eighty miles below, the Red river from the west, unite their waters with the Mississippi. Red River takes its rise in the Mexican dominions, and runs a course of more than 2,000 miles.
Hitherto, the waters in the wide regions of the west have been congregating to one point. The "Father of Waters," is now upwards of a mile in width, and several fathoms deep. During its annual floods, it overflows its banks below the mouth of the Ohio, and penetrates the numerous bayous, lakes, and swamps, and especially on its western side. In many places these floods extend thirty or forty miles into the interior. But after it receives the Red river, it begins to throw off its surplus waters, which flow in separate channels to the gulf, and never again unite with the parent stream. Several of these communications are held with the ocean at different and distant points.
Ohio River. The Ohio river is formed by the junction of the Alleghany and Monongahela, at Pittsburg. The Alleghany river rises not far from the head of the western branch of the Susquehannah, in the highlands of McKean county, Pennsylvania. It runs north till it penetrates Cataraugus county, New York, then turns west, then southwest, and finally takes a southern course to Pittsburg. It receives a branch from the Chatauque lake, Chatauque county, New York. The Monongahela rises near the sources of the Kenhawa, in western Virginia, and runs north till it meets the Alleghany.
The general course of the Ohio is southwest. Its current is gentle, and it receives a number of tributaries, which are noticed in the States where they run.
The Valley of the Mississippi has been arranged by Mr. Darby, into four great subdivisions.
1. The Ohio Valley, length 750 miles, and mean width 261; containing 196,000 square miles.
2. Mississippi Valley, above Ohio, including the minor valley of Illinois, but exclusive of Missouri, 650 miles long, and 277 mean width, and containing 180,000 square miles.
3. Lower Valley of the Mississippi, including White, Arkansas, and Red river vallies, 1,000 miles long, and 200 wide, containing 200,000 square miles.