From here one of the shortest rivers in the country flows into the longest river. The Roe River ranks as one of the shortest rivers at only 201 feet in length. The Missouri River is the longest in the country, stretching 2,540 miles, 200 miles longer than the Mississippi River. The Roe River gets its name from the term “Roe,” which commonly means fish eggs. Visitors can learn about the various stages of fish growth and the hatchery process at Giant Springs Fish Hatchery Visitor Center, where one million rainbow trout are raised each year, and may also enjoy feeding the fish in the nearby show pond.