Yijmas, a nation of American Indians on both sides of the Colorado near its junction with the Gila, calling themselves the Sons of the Eiver. They are also termed Cuchans. They were early known to the Spaniards, and were visited by Father Kühn in 1701, and by Sedelmayr in 1744 and 1748. In 1780 Spanish settlements were begun among them with two Franciscan missions, Purisima Concepcion and San Pedro y San Paulo; but as the Spaniards occupied nearly all their fertile lands, the Yumas in July, 1781, massacred all the whites. In 1791 their number was estimated at 3,000. After their territory came within the limits of the United States they were visited by Lieut. "Whipple in October, 1849. They were then friendly to whites, inhabited rude excavated huts, with roofs of boughs supported by posts, and lived partly by hunting and fishing and partly on maize, melons, and pumpkins raised by the women, and on mezquite beans and grass seed gathered by them. The women made water-tight baskets and rude pottery, and a kind of brandy from the mezquite. They had horses and dogs, but no other animals. Round bits of shell pierced as beads served for money and ornament The men wore a breech cloth, the women a bark fringe apron; all painted. The hair was cut at the eyebrows, but worn very long behind.

They were well formed, active, and intelligent. They have been faithful, refusing to join other tribes against the Americans, except in 1853, when under Antonio Gana they rose against the whites, but were defeated by Gen. Heintzelman. Since Fort Yuma was placed near them the women have been completely debauched, so that the whole.tribe is now diseased. They have long been at war with the Maricopas, Pimas, and Papagos. In 1828 they were nearly annihilated by their enemies, and the remnant of the nation fled to the Mohaves, where they remained till 1845, when they returned to their original hunting grounds. They renewed war with the Maricopas in 1849, but in 1857 they and their allies were defeated at Maricopa Wells, and out of 100 Yuma braves only 6 escaped. Under the act of March 3, 1865, and executive orders of Nov. 22, 1873, and Nov. 16, 1874, a reservation of 200 sq. m. was set apart for the Mohaves, Cocopas, Hualapais, Yumas, and Chemehueves; but though the influx of whites has narrowed their tillable lands and hunting grounds, and the mezquite is used for fodder, they shrink from going on the reservation, and live chiefly by menial labor.

They are now (1876) reduced to 930. The Mohaves, Cocopas, Yavapai, and San Diego Indians are allied in language to the Yumas, and Pimentel traces a connection between the Yuma and Pima tongues.