The Canadian River is the longest tributary of the Arkansas River in the United States. It is about 906 miles (1,458 km) long, starting in Colorado and traveling through New Mexico, the Texas Panhandle, and Oklahoma. The drainage area is about 47,700 square miles (124,000 km2).The Canadian is sometimes referred to as the South Canadian River to differentiate it from the North Canadian River that flows into it. Source: Wikipedia