The Arkansas River is a major tributary of the Mississippi River. It generally flows to the east and southeast as it traverses the U.S. states of Colorado, Kansas, Oklahoma, and Arkansas. The river's source basin lies in the western United States in Colorado, specifically the Arkansas River Valley, where the headwaters derive from the snowpack in the Sawatch and Mosquito mountain ranges. It then flows east into the Midwest via Kansas, and finally into the South through Oklahoma and Arkansas. At 1,469 miles (2,364 km), it is the sixth-longest river in the United States, the second-longest tributary in the Mississippi–Missouri ... Source: Wikipedia