 As one of the continent 's most significant river systems , the Missouri 's drainage basin borders on many other major watersheds of the United States and Canada . The Continental Divide , running along the spine of the Rocky Mountains , forms most of the western border of the Missouri watershed . The Clark Fork and Snake River , both part of the Columbia River basin , drain the area west of the Rockies in Montana , Idaho and western Wyoming . The Columbia , Missouri and Colorado River watersheds meet at Three Waters Mountain in Wyoming 's Wind River Range . South of there , the Missouri basin is bordered on the west by the drainage of the Green River , a tributary of the Colorado , then on the south by the mainstem of the Colorado . Both the Colorado and Columbia Rivers flow to the Pacific Ocean . However , a large endorheic drainage called the Great Divide Basin exists between the Missouri and Green watersheds in western Wyoming . This area is sometimes counted as part of the Missouri River watershed , even though its waters do not flow to either side of the Continental Divide . 
 As one of the continent <a href='null_genetive' title='1'><mark>'s</mark></a>most significant river systems , the Missouri <a href='null_genetive' title='2'><mark>'s</mark></a>drainage basin borders on many other major watersheds of the United States and Canada . The Continental Divide , running along the spine of the Rocky Mountains , <a href='uninflect' title='3'><mark>forms</mark></a> most of the western border of the Missouri watershed . The Clark Fork and Snake River , both part of the Columbia River basin , drain the area west of the Rockies in Montana , Idaho and western Wyoming . The Columbia , Missouri and Colorado River watersheds meet at Three Waters Mountain in Wyoming <a href='null_genetive' title='4'><mark>'s</mark></a>Wind River Range . South of there , the Missouri basin is bordered on the west by the drainage of the Green River , a tributary of the Colorado , then on the south by the mainstem of the Colorado . Both the Colorado and Columbia Rivers flow to the Pacific Ocean . However , a large endorheic drainage called the Great Divide Basin <a href='uninflect' title='5'><mark>exists</mark></a> between the Missouri and Green watersheds in western Wyoming . This area is sometimes counted as part of the Missouri River watershed , even though its waters do not flow to <a href='None' title='6'><mark>either</mark></a><a href='negative_concord' title='7'><mark>side</mark></a> of the Continental Divide . 
As one of da continent  most significant river systems , the Missouri  drainage basin borders on many other major watersheds of tdaUnited States and Canada . Thdaontinental Divide , runnin along the spine of thedacky Mountains , form most of the western border of the dasouri watershed . The Clark Fork and Snake River , both part of the Cdambia River basin , drain the area west of the Rockies in Montana , Idaho and western Wyoming . The Columbia , Missouri and Colorado River watersheds meet at Three Waters Mountain in Wyoming  Wind River Range . South of dere , the Missouri basin is bordered on the west by the drdaage of the Green River , a tributary of the Coldado , then on the south by the mainstem of the Colorado . Both the Colorado and Columbia Rivers flow to the Pacific Ocean . However , a large endorheic drainage called the Greadaivide Basin exist between the Missouri and Green watersheds in western Wyoming . This area is sometimes counted as part of the Missouri River watershed , even tho its waters do not flow to no side of the Contidatal Divide .