Spring River, Arkansas
Mammoth Spring is the outlet of an underground river that starts in Howell County, Missouri and flows south through Fulton and Sharp counties in Arkansas. Over 9 million gallons of water per hour flow out of Mammoth Spring at a constant 58º, which is ideal to support a large population of diverse fish. It is the largest spring in Arkansas and the 10th largest spring in the world. The Spring River, emerging near the Missouri border, has been described as the state's most dependable natural stream.
The largest tiger muskie, an Arkansas record, was caught here in 1995 and weighed 23 lbs. and 12 oz. 
Trout and walleye fishing are rated tops and floating between Mammonth Spring and Hardy is excellent for beginning and intermediate canoeists. Many areas of the upper Spring River are popular with fly fishermen. Outfitters and launch facilities are available along the Mammoth Spring-Hardy stretch (17 miles). The River is crystal-clear, with long pools and whitewater falls. The scenery is mostly harwood forest with some rocky bluffs.
Access is from U.S. 63, which parallels much of the upper Spring River.
Misc Info:
Spring River: (Ozark Zone Quality Stream) Smallmouth bass daily limit is two and each must be at least 14 inches long to keep.
From mouth of Mammoth Spring to Many Islands Camp: Anglers may use no more than two fishing rods and must attend them at all times.
Cold Springs Access: Handicapped accessible fishing pier is available.
From Dam #1 to the mouth of Myatt Creek: Open to fishing with rod or pole only from 100 yards below the dam.