'Tis the Missouri River. The Missouri River forms nearly 75 mi (121 km) of the state's northeastern boundary. The Kansas River (locally known as the Kaw), formed by the junction of the Smoky Hill and Republican rivers at appropriately-named Junction City, joins the Missouri at Kansas City, after a course of 170 mi (270 km) across the northeastern part of the state. The Arkansas River (pronunciation varies), rising in Colorado, flows with a bending course for nearly 500 mi (800 km) across the western and southern parts of the state. It forms, with its tributaries (the Little Arkansas, Ninnescah, Walnut, Cow Creek, Cimarron, Verdigris, and the Neosho), the southern drainage system of the state. Other important rivers are the Saline and Solomon Rivers, tributaries of the Smoky Hill River; the