It is found in about 65 percent of the state's lakes and many of its slow streams, including the backwaters of the Mississippi. It is rare in the Lake Superior drainage.
Appearance varies considerably among individuals, as is true with most sunfish.
Most bluegill are light to dark olive, though older fish may have a purplish tinge. Cheeks and gill covers are often bluish and the ear flap is black. The rearward edge of the soft portion of the dorsal fin carries a dark blotch. Breeding males are marked by bright blue and orange. Females and younger fish are less colorful and are often marked by dark vertical bars on their olive backs.