 The Missouri 's largest tributaries by runoff are the Yellowstone in Montana and Wyoming , the Platte in Wyoming , Colorado , and Nebraska , and the Kansas – Republican / <unk> Hill and Osage in Kansas and Missouri . Each of these tributaries drains an area greater than 50 @,@ 000 square miles ( 130 @,@ 000 km2 ) , and has an average discharge greater than 5 @,@ 000 cu ft / s ( 140 m3 / s ) . The Yellowstone River has the highest discharge , even though the Platte is longer and drains a larger area . In fact , the Yellowstone 's flow is about 13 @,@ 800 cu ft / s ( 390 m3 / s ) – accounting for sixteen percent of total runoff in the Missouri basin and nearly double that of the Platte . On the other end of the scale is the tiny <unk> River in Montana , which at 201 feet ( 61 m ) long is one the world 's shortest rivers . 
