The lake is located in Ralls and Monroe Counties of Missouri, 28 miles southwest of Hannibal, MO and 120 miles northwest of St. Louis.
At normal pool Mark Twain Lake encompasses 18,600 acres, providing a variety of fishing opportunities for large and small mouth bass, crappie, walleye, catfish, bluegill and others.
Approximately 45,000 of land and water are available for hunting. Species available for hunting include dove, quail, squirrel, deer, wild turkey, rabbits and waterfowl.
Originally known as the Joanna Dam, the Clarence Cannon Dam is a 138 ft high and 1,940 ft long combination concrete gravity embankment dam. The dam contains 450,000 cu yd. of concrete and 3,000,000 cu yd. of earth-fill.
The Clarence Cannon Dam contains a hydroelectric power plant, with two generators, capable of producing up to 58 MW of power, or enough to supply a town of 20,000 people. When both units are operating at capacity up to 5,400,000 US gallons of water pass through the turbines per minute. A regulation dam (or re-reg dam known by locals), is located 9.5 miles downstream from the main dam, creates a storage pool that can be used for pumped-storage hydroelectricity. When demand for electricity is low, power from other sources can be used to pump water back from the tailwater to the lake. This water can then be re-cycled through the turbines when energy is in high demand
Facilities include 6 major boat ramps, 29 hunter/fisherman access areas, 2 full-service marinas, 2 beaches, 3 campgrounds with 440 sites, 2 group campgrounds, picnic shelters, playgrounds and trails. There are also 30,000 acres of land and water open for hunting in season.
With over 18,000 acres of water, Mark Twain Lake is a suitable location for any type of water recreation. Anglers will find catfish, bass, crappie, walleye, bluegill and sunfish. Timber has been left in the upper ends of the lake and in selected coves to improve fish habitat. Excellent fishing for crappie, catfish, largemouth bass, bluegill, carp, walleye and perch awaits you at Mark Twain Lake. The lake has many quiet coves where you can spend peaceful days fishing and relaxing.