This stream derives its name from the Kanza or Kaw tribe of Native American, which lived on its banks from time immemorial. One of the earliest references to the stream was by Antonio de Herraray Tordesillas, historiographer to the King of Spain. Marquette mentions the Kanza, Native American tribe in 1673. A map of the British and French settlements in North America, published in 1758, gives the stream as the "Padoucas river".
The Kansas river is formed by the junction of the Smoky Hill River and Republican River at Junction City and flows in a general easterly direction through Geary County and Riley County, forms the boundary between Pottawatomie County and Wabaunsee County, crosses Shawnee County, forms the boundary between Jefferson County and Douglas County, and of Wyandotte County and Johnson County in part, and empties into the Missouri River at Kansas City. From Junction City to the mouth is about 240 miles.