Green River ,.I. A considerable stream which rises in Lincoln co., Ky., flows W. past the Mammoth cave, and, after receiving Big Barren river, bends N. W. and enters the Ohio 9 m. above Evansville in Indiana; length, nearly 300 m. It is 200 yards wide at its mouth, and in the lower part of its course is navigable by steamboats at all seasons, while, by means of dams and locks, small steam vessels can ascend to Greensburg, a distance of 200 m. The upper part of its valley is occupied by cavernous limestone, and the lower abounds in coal. II. One of the constituents (properly the upper continuation) of the Colorado of the West. It rises in the Rocky mountains near Fremont's peak, in the W. part of Wyoming territory, in about lat. 43° 15' N., Ion. 109° 45' W., flows S., turns S. E. through the N. E. corner of Utah, entering the N. W. corner of Colorado, then bends S. W. and reenters Utah, and afterward pursues a general S. course to its junction with the Grand. Its entire course is about 500 m. Besides numerous affluents which it receives in Wyoming, the principal tributaries are the Yampah or Bear and the White from the east, and the Uintah, White, Little White, and San Rafael from the west. Green river for the greater part of its course flows through deep and precipitous canons.

It first enters the Uintah mountains in the extreme N. W. corner of Colorado, at a point called Flaming Gorge, just below which the walls of the canon are nearly 1,500 ft. high. The stream is swift, the descent being in places 20 ft. to the mile. Rapids and cataracts, some of them of great height, are frequent. There is generally on the one side or the other a narrow strip of land forming the valley of the river, but for considerable distances the walls rise perpendicularly from the water's edge to the height of 5,000 or 6,000 ft., and at one point of 6,500 ft.