Rio Colorado, Or Colorado River Of The West Colorado, a river formed by the junction of the Green and Grand rivers in S. E. Utah, about lat. 38° N., lon. 110° W. Green river rises in the Rocky mountains near Fremont's peak, in the W. part of Wyoming territory, 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. Among its tributaries are the Yampah or Bear, the White, Uintah, and San Rafael. Grand river rises in the Rocky mountains, in Middle park, W. of Denver, Colorado, and has a S. W. course. Its principal tributaries are the South fork or Gunnison, Rio San Miguel, and Dolores. Below the junction the Colorado flows S. W. into Arizona. Near the 36th parallel it makes a bend, and pursues a winding course in a general W. direction to the border of Nevada, whence it flows S., separating Arizona from Nevada and California, and Sonora from Lower California, until it discharges its waters into the gulf of California. The principal tributaries from the east are the San Juan in Utah, and the Colorado Chiquito, or Little Colorado, Bill Williams fork, and Gila, in Arizona. From the west the only noticeable affluents are the Dirty Devil and Escalante in Utah, the Paria, Ta-peat's river, and the Kanab, from Arizona, and the Rio Virgen, which enters from Nevada. In many respects the Colorado is remarkable.

Above Callville, Nevada, the river, as well as its tributaries, flows through deep canons, the walls of which in some places rise nearly 7,000 ft. above the surface of the water. Upon the generally treeless plateaus divided by these rivers rise other terraces, with nearly perpendicular walls 1,000 ft. or more in height. Both the loftier and lower plateaus are covered with massive ruins of once populous walled towns and cities, which are supposed to have been occupied by the Toltecs, the predecessors of the Aztecs. The Moqui Indians in N. E. Arizona, near the Colorado Chiquito, are supposed to be descendants of this race. The Green river 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 cafion 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. Above the junction of the Grand there is generally on the one side or the other a narrow strip of land forming the valley of the river. The extent of these canons is over 500 m. The largest and most noted of them, the Grand canon, extends down the river, from the mouth of the Little Colorado, a distance of more than 200 m.

The height of the walls varies from 4,000 to 7,000 ft. The channel is from 50 to 300 ft. in width, and the descent of the stream from 5 to 200 ft. to the mile. "The banks of the river," says Major Powell, "are cliffs of solid rock, often vertical for hundreds or thousands of feet; but in places these cliffs or walls of the canon are broken down in steep slopes, and in other places they are terraced on a grand scale, the glacis often being from a half mile to a mile in width, and the step to a higher terrace several hundred feet. There is no proper flood plain along the river through this canon, but usually rocks have fallen down from the walls on one or both sides, so as to form a talus, varying from 25 to 300 ft. in height. But in other places there is no talus, the river filling the channel from wall to wall. Numerous streams come down from the high plateaus on either side, each having its own winding canon, and these have tributary canons, making the topography adjacent to the river exceedingly intricate." In the valley of the Colorado below the canons is found a large extent of fertile bottom land, easily cultivated by artificial irrigation. This valley varies in width from 3 to 8 m. The greater part of it is covered with timber, chiefly cottonwood and mezquite.

Just below Callville is the Black canon, about 25 m. long, with walls in places from 1,000 to 1,500 ft. high, which is the only canon below the Grand canon. After receiving the Gila, the Colorado takes a sudden turn westward, forcing its way through a chain of rocky hills, 70 ft. high and about 350 yards in length. In this passage it is about 600 ft. wide, but soon expands to 1,200 ft., which it retains. After sweeping round 7 or 8 m., it resumes its S. direction, and pursues a very tortuous course of nearly 180 m. to its mouth. The bottom lands are here from 4 to 5 m. wide, and covered with a thick forest. - The length of the Colorado, from the sources of Green river, is about 2,000 m. It is navigable for steamers to Callville, 612 m.; and it is thought that navigation may be carried to the foot of Grand canon, 57 m. above. Arnold's point, 35 m. from the mouth, is the head of navigation at low water (winter) for vessels drawing 9 ft. To the head of tide water, 40 m., navigation is difficult and dangerous, from the rapid rise of the tide and the shifting of the channel. Above this point the current, obstructed by small snags and sawyers, runs from 1 to 3 m. an hour (in fres'hets from 2 to 6 m.) through a narrow channel. The rise of ordinary spring tides is 12 ft.

In freshets the river rises at Arnold's point 15 ft. above low water, and in seasons of unusual height it flows back over the California desert, filling up several basins, and what is known as New river, in Lower California. This water remains one or two years, when it is swallowed up by the sands, or evaporated by the hot sun. At the mouth of the river a good harbor was discovered in 1864. It consists in fact of a second mouth of the Colorado, which branches off some 80 m. up, and empties in such a way as to afford secure shelter from the terrible "borers " of the gulf. It is from 50 to 80 yards broad, and with perpendicular banks of hard clay some 25 ft. high at low tide. At high tide the banks overflow a few inches, but the anchorage remains good. About 6 m. up there is an abrupt fall extending across the stream, some 4 or 5 ft. high at low water, but disappearing at high tide. The depth of water in this singular harbor at low tide is from 15 to 25 ft. This harbor is now used almost exclusively by the vessels in the Colorado trade.

Their cargoes are here transferred to the small river boats and barges, and they here receive their outward-bound freights. - In 1540 Fernando Alarcon, in a voyage to explore the gulf of California, by order of the viceroy of Spain, discovered the mouth of the Colorado, which he describes as "a very mighty river, which ran with so great a fury of stream, that we could hardly sail against it." He fitted out two boats with which he sailed up the river. Father Kino, about the year 1700, also sailed up to the confluence with the Gila, where he established a mission. Lieut. Ives explored the Colorado below the canons in a steamer in 1857. The first descent through the canons was made in 1867 by James White, from a point on Grand river about 30 m. above its junction with the Green. White, Capt. Baker, an old miner and an ex-officer of the confederacy, and Henry Strole were prospecting for gold in the W. portion of Colorado. Having met with ill success, and having lost Capt. Baker during an attack by Indians in a lateral cafion of the Grand, which they had descended for water, White and Strole determined to attempt an escape by the river rather than retrace their steps through a country beset by Indians. They constructed a frail raft of a few pieces of drift wood, and, having secured their arras and provisions, commenced their downward journey on the night of Aug. 24. Subsequently the raft was generally secured by night and allowed to drift only during the day.

On the 28th, while descending a cataract, Strole was drowned, and all the provisions were washed overboard. White continued the journey alone, amid great peril from cataracts, rocks, and whirlpools, hemmed in by the walls of the canon, and 10 days after reached Call-ville, having tasted food but twice during that period. Once he obtained a few green pods and leaves from bushes growing along the stream, and the second time he was given some food by Yampais Indians who occupied a low alluvial strip of land along the river, the trail to which from the plateau was known only to themselves. In 1869 a corps fitted out by the United States government, under the command of Prof. J. W. Powell, started in boats from the upper Green river in Wyoming territory, and, after much peril and many hair-breadth escapes, reached Callville, having passed through the whole length of the canons. In 1871 another expedition under Prof. Powell was fitted out for the exploration of the Colorado valley. The portion of the river embraced in this exploration is about 1,000 m. in length, commencing where the Union Pacific railroad crosses Green river, and extending down the stream to the end of the Grand canon. E. and S. of the river the survey runs back from 10 to 40 m. from the stream.

On Jan. 1, 1873, the exploration had been completed of the region N. and W. of the Colorado, drained by its tributaries, from the Rio Virgen on the south to the Dirty Devn on the north, embracing a territory 300 m. long and 175 m. wide. N. of this a general reconnoissance had also been made of the territory between the Wasatch mountains and San Pete valley on the west and Green river on the east, embracing the valley of the Uintah, the ranges of mountains and extensive plateaus.lying S., the valley of Price river, the Wasatch plateau, the valley of the San Rafael, and the plateau and mountains in which this river has its sources. The survey of the region embraced in Prof. Powell's plan is to be completed in 1875, when the entire valley of the Colorado will have been explored, the portion above the Union Pacific railroad and that below the Grand canon having been already surveyed.