Arizona, till 1906 a territory of the United States, bounded N. by Utah, E. by New Mexico, S. by the republic of Mexico (Sonora), and W. by California and Nevada. Its western boundary is mostly formed by the Colorado of the West. This river traverses the NW. part of Arizona in a deep and narrow water-worn channel (the Grand Canon), more than 300 miles long, and nowhere less than a mile below the surface of the surrounding country. Arizona had an area of 112,920 sq. m.; it was thus nearly as large as Italy. It is in general a region of high plateaus, traversed by various mountain-ranges, presenting abundant evidence of not remote volcanic action. In the SW. the country has a desert character, and in all parts the rainfall is decidedly limited - 14.21 inches annually at Fort Defiance. In various parts there are extensive lava-beds. The whole region lies in the drainage basin of the Colorado, the chief affluents being the Gila, the Bill Williams, and the Colorado Chiquito. The water-supply over large areas of Arizona is mainly derived from deep natural wells and ' water-holes.' It is believed that fully 10,000,000 acres of ground might be profitably irrigated. The country is in general extremely healthful; but in the SW. the summer heat is excessive, and malarial fevers are not unknown upon the bottom-lands of the Lower Colorado.

Maize, barley, and wheat are the leading products. Arizona is an important seat of gold and silver mining. Copper is also mined and smelted very largely. Coal has been obtained. Rock-salt, lead, and other valuable mineral deposits are found in almost every part of the country. The principal towns are Phoenix, the capital, and Tucson. Some interesting old Indian towns, or pueblos (Moquis), still remain, with their remarkable native semi-civilisation. This region was first visited by Spaniards in 1570. After 1821 the country was a part of Mexico until 1848, when most of it passed to the United States, the transference being completed in 1853 by the 'Gadsden Purchase.' The territory was organised in 1863. In 1870 the population was 9658; in 1900, 122,900. In 1906, including the adjoining territory of New Mexico, it was made a state of the Union. Total area, 235,380 sq. m.; pop. (1900) 318,210. See New Mexico.