Colorado (Co-lo-rah'do; Span, 'reddish'), a remarkable river of North America, formed in 39o 17' N. lat., 109o50' W. long., by the union of the Grand and Green rivers, rising, one in Colorado state, the other in Wyoming. Below the junction, the main affluent in Utah is the San Juan, and in Arizona the Colorado Chiquito or. Flax River, the Bill Williams, and the Rio Gila, all from the left. The only important affluent the Colorado receives from the right is the Rie Virgen. From the junction of the Grand and Green, the general course of the stream is to the south-west, through the southern part of Utah and the north-west of Arizona; and it afterwards separates Arizona from Nevada and California. The lower part of its course is in Mexican territory, where it flows into the north extremity of the Gulf of California. The most striking features of the Colorado basin are its dryness, and the deeply channelled surface of the greater part of the country. Almost every stream and watercourse, and most of all the Colorado itself, has cut its way through stratum after stratum of rock, until now it flows, in a great part of its course, at the bottom of a deep trench or canon. For nearly 400 miles below the mouth of the Colorado Chiquito, the main stream thus makes its way through a great plateau, forming what is called the Grand Canon of the Colorado, one of the most remarkable ravines in the world. The canon-walls throughout the upper part of the great canon are from 4000 to 7000 feet in height, and are often nearly perpendicular. This over-drained river basin has an area of 240,000 sq. m. The whole course of the river below the junction is about 900 miles; to its remotest sources it is 2000 miles. Navigation, though much impeded by rocks and sand-bars, is possible for light-draught steamers for over 600 miles. See Powell's Canyons of the Colorado (1893), Dutton's book on the geology, and Delleu-baugh's Romance of the Colorado (1903).
Colorado River of Texas rises by many head-streams in north-west Texas, winds 900 miles south-eastward, and discharges its waters by two main outlets into Matagorda Bay. It is little used for navigation. Its valley is fairly fertile and supplied with timber.
Colorado, a state of the American Union, in 37°-41°N. lat., and 102°-109° W. long., traversed from north to south by ranges of the Rocky Mountains. It takes its name from the river Colorado, to the basin of which all the western slope of the state belongs, as the eastern does to the Mississippi valley; while part of the south is drained by the Rio Grande and its head-streams. The area is 103,645 sq. m., or rather more than half that of France, Colorado being fifth of the states in size. The high plains and over-drained mesas to the west are not clearly marked off from the mountain-region; and much of the western slope is actually mountainous. The eastern slope, which embraces about two-fifths of the whole state, is, apart from the foothills skirting the flank of the mountain-region, an open and comparatively treeless plain, with a surface singularly monotonous, and for the most part devoted to the pasturage of cattle and sheep. This level region averages 5000 feet in altitude, and its lowest point is 3000 feet above sea-level. The mountain region contains more than a hundred peaks exceeding 13,000 feet, the loftiest being Blanca Peak (14,464 feet). Six passes cross mountain-ranges at points over 12,000 feet high; the Argentine Pass is 13,000 feet in altitude. Railways are led across many of these passes. A marked feature of the mountain-region is presented in the parks, or rich mountain-valleys, often very spacious, and generally bearing evidence of being the dried basins of lakes. The central mountain-region, with its parks, canons, and hot springs, and its rich mineral deposits, has attracted most attention; the western part of the state is far less accessible and less developed. The rainfall is small; but a good many important streams take their rise in the state, including several tributaries of the Colorado; the Arkansas and South-Platte, flowing to the Mississippi; and the Rio Grande. Extensive and important irrigation-works are fed by some of these streams. From the dryness of the air, Colorado has a great reputation as a health-resort. The medicinal and thermal springs are numerous. A disease called ' mountain fever' is endemic in some places. Agriculture is remunerative in all sections where irrigation can be effected. Insect-plagues, including the Colorado potato-beetle, have proved very destructive; the Rocky-mountain locust has of late been comparatively harmless.
The discovery of gold (1858) in the neighbourhood of Pike's Peak led to the first important settlements in this region. Since 1873 the silver production has far exceeded that of gold, and the state took rank as the first in out-turn of silver, second or third in its gold, and first or second in the production of the precious metals in general. The depreciation of silver and the currency legislation of 1893 led to the closing of some of the silver-mines, and on the other hand a development of gold-mining took place, so that from 1897 Colorado was the chief gold-producing state of the Union, and from 1900 onwards produced annually twice as much as California. In the working of the silver ores much lead is obtained. There are great beds of coal. Iron and Bessemer steel rails are among the manufactures; copper, cement, fireclay, and manganese are wrought; and there are thirty petroleum wells near Florence. Not quite one-half of this region was acquired by the United States from France in 1804; the remainder was ceded by Mexico in 1848. The southern part has a small Spanish-speaking population, partially of Indian descent. Colorado was organised as a territory in 1861, and was admitted as a state in 1876. The principal towns are Denver, the capital (106,713), and Pueblo (24,558). Pop. of Colorado (1860) 34,277; (1870) 39,864; (1880) 194,327; (1885) 243,910; (1890) 412,198; (1900) 539,700.