Knox Lake is located about 1½ miles northeast of Fredericktown and can be accessed via State Route 95. The marina and main boat ramp are located on the lower section of the reservoir along Armentrout Road. Other boat ramps are located off County Road 5 in the upper section of the reservoir. Knox Marine is located on the north end off of Old Mansfield Rd.
Knox Lake was built by the ODNR Division of Wildlife in 1954. The reservoir, created by damming the Kokosing River, was built primarily for recreation. The reservoir is 469 acres in size and has 11.4 miles of shoreline. Maximum depth is over 24 feet near the dam, although much of the water is 12 feet or less. Bottom composition is made up of rock and gravel in the lower section and mud and silt in the upper section. The upper section of the reservoir was purposely left full of standing timber to provide natural cover to enhance fishing. In the lower basin trees have been felled along the shoreline to provide additional cover.
The Division of Wildlife maintains the parking lots, picnic areas, boat ramps, docks and rental boat slips. The reservoir has a 10 horse power limit on outboard motors. However, larger outboard motors may be operated at no wake or idle-speed only. The diverse bottom composition and cover from stumps and fallen trees provide excellent habitat for a number of sport fish. Knox Lake consistently ranks as one of the premier largemouth bass fisheries in central Ohio. Channel catfish are stocked periodically, and the crappie, and bluegill also provide excellent fishing opportunities for anglers.