IDK..... check out www.pbs.org/lewisandclark to find out
People along several river make that claim. Most common in the U.S. is the Mississippi River. Roads along it are called "Great River Road". See more about the Mississippi River at link below
Total length of Missouri River is 2341 miles and total length of Mississippi River is 2320 miles. Missouri River is longer then Mississippi River.
Missouri River.
The Missouri does, the Colorado does not. It empties instead into the Sea of Cortez.