The oak-hickory forests surrounding Coffeen Lake are representative of the native cover found within the Southern Till Plain Natural Division of central and southern Illinois. Soils are of loess and till, rather light and a characteristic "claypan" can be found. Pre-settlement vegetation was a mixture of 60 % forest to 40% prairie and wetlands. A variety of trees, woodland and prairie plants cover the slopes of the stream valley. Visitors may also find a diverse wildlife community. Muskrats, turtles, herons and mussels are seen in or near the water. Red-tailed hawk, blue jay or a dragonfly might be seen in the air. Bobwhite, coyote, white-tailed deer and black rat snake are common to the area. The opportunity to observe and enjoy the area's rich wildlife heritage is available. Coffeen Lake boasts an excellent largemouth bass and channel catfish population. Twenty-two species of fish are present in the lake, but most anglers seek largemouth bass, white crappie, channel catfish and striped bass. The lake is deeper than most Illinois lakes, averaging nearly 19 feet with a maximum depth of 59 feet. Coffeen Lake has nearly 50 miles of shoreline. Power plant operation noticeably influences fish activity and fishing success. Fish growth appears to be faster than in many other lakes, however. The Main Access (lower pool) provides a two lane ramp and a newly constructed parking lot with a handicap accessible loading platform and reserved handicap parking stalls. The North Access (upper pool) provides a newly constructed single lane ramp and a handicap accessible courtesy dock and parking lot. Motors of 25 horsepower or less are allowed to operate on the lake. Boats with motors larger than 25 horsepower are allowed on the lake, but are restricted to trolling motor operation only. However, motors larger than the 25 horsepower can be used for loading and unloading a trailered watercraft, provided the watercraft over the horsepower limit is operated at a no-wake speed within 150 feet of the loading ramp itself. Bank fishing is available at all boat access area. Considerable acreage is open for bank fishing where parking is present. Posted site specific regulations for bass and crappie are enforced. All fishing tournaments must be scheduled through the site office. Toilets, drinking water and picnic facilities are available at the main access area. A private campground is located just to the north of the main access area. Bait, supplies and food can be obtained there.
Coffeen Lake State Fish and Wildlife Area is an Illinois state park on 297 acres (120 ha) in Montgomery County, Illinois, United States.