The Canadian River, the largest tributary of the Arkansas River, rises in the Sangre de Cristo Mountains in southern Las Animas County, Colorado, near Raton Pass and the boundary line with Colfax County, New Mexico (at 37°01' N, 105°03' W), and flows south and southeastward, separating theLlano Estacado from the northern High Plains. It is roughly 760 miles long; a stretch of about 190 miles is in Texas. The river is dammed to form the Conchas and Ute reservoirs in northeastern New Mexico before it enters Texas at about the midpoint of the western boundary of Oldham County. The Canadian crosses thePanhandle, flowing eastward and northeastward through Oldham, Potter, Moore, Hutchinson, Roberts, and Hemphill counties. Most of the river's course across the Panhandle passes through a gorge 500 to 800 feet below the plateau. Particularly in its lower reaches in Oklahoma, the riverbed contains great amounts of quicksand; this and the deep gorge make the river difficult to bridge. A tributary, the North Canadian, heads in Union County, New Mexico (at 36°30' N, 102°09' W), and flows briefly into the northern Texas Panhandle before continuing on to its confluence with the river in McIntosh County, Oklahoma (at 36°30' N, 101°55' W). After crossing the state line back into Oklahoma, the Canadian River flows generally southeastward to its mouth on the Arkansas River, twenty miles east of Canadian in Haskell County, Oklahoma (at 35°27' N, 95°02' W).

According to some sources, the river's name came from early explorers who thought that it flowed into Canada. Among the Canadian's principal tributaries in Texas are Big Blue, Tallahone, Red Deer, Pedarosa, Punta Agua, Amarillo, Tascosa, and White Deer creeks. The Texas portion of the Canadian River is noted for archeological sites where extensive remains of Pueblo Indian culture have been found (seeANTELOPE CREEK PHASE). Some historians have said thatQuivira Province, long sought byFrancisco Vásquez de Coronado, was on the Canadian. The Canadian is probably the stream thatJuan de Oñate called the Magdalena in 1601. The area was Comanche country until the latter part of the 1800s, but the stream was well known to the Comancheros (seeCOMANCHERO), toJosiah Gregg, and to others engaged in trade out of St. Louis or Santa Fe. Lt.James William Abert of the United States Army Corps of Topographical Engineers explored the river in 1845 and made an extensive report of its physical features and of the Indians whom he encountered. With the decimation of thebuffalo, cattlemen replaced Indians in the area, and, except for oil developments, the Canadian valley in Texas remained in 1949 principally a ranching area.

The river is dammed to formLake Meredith forty miles northeast of Amarillo near Sanford in Hutchinson County. ThePanhandle Water Conservation Authority as early as 1949 was contemplating construction of Sanford Dam to create a reservoir of some 1,305,000 acre-feet capacity that would furnish a municipal water supply for eleven Panhandle cities and serve the secondary purposes of flood control, soil conservation, recreation, and promotion of wildlife; actual impoundment of water did not begin until 1965. Lake Meredith is named for A. A. Meredith, who was executive secretary of theCanadian River Municipal Water Authority. An aqueduct to serve Pampa, Amarillo, Lubbock, Lamesa, Borger, Levelland, Littlefield, O'Donnell, Slaton, and Tahoka was estimated to cost $54 million. Cities purchasing the water would repay the major part of the cost of the project over a period of fifty years. TheCanadian River Compact Commissioner, appointed in 1951, negotiates with other states regarding the water of the Canadian. The National Park Service assumed management of recreational facilities at Lake Meredith in 1965.