Everyone has heard of the worlds longest river, the Nile, measuring a staggering 4,132 miles. However, I doubt most have heard of the worlds shortest river, at only 201 feet long. Named Roe River, it flows from its headwaters in Giant Springs, Montana, before merging almost immediately with the Missouri River. If we were to place a typical American river barge at the beginning of the river, it would only have to travel 6 feet before entering the Missouri.