Chemung, elevation 896 feet (273 meters), is an unincorporated census-designated place in McHenry County, Illinois, United States. As of the 2010 census, its population was 308.
A post office called Chemung was established in 1845, and remained in operation until it was discontinued in 1943. The name Chemung is said to be a Native American word meaning "big horn".
The small, unincorporated town is located approximately 3.14 miles west of downtown Harvard, Illinois at the junction of Illinois Route 173, Oak Grove Road (County Highway A-20) and Island Road (the continuation of Oak Grove Road south of Route 173). The town staddles the line between Chemung Township and Dunham Township. In terms of geographic coordinates, Chemung is located at 42°24′55″N 88°40′00″W / 42.41528°N 88.66667°W (42.4152964, -88.6667668)  In terms of the Public Land Survey System, Chemung is found in Sections 4 and 5, Township 45 North, Range 5 East; and Sections 32 and 33, Township 46 North, Range 5 East of the Third Principal Meridian. Lawrence Creek flows along the west side of Chemung in a generally northeast to southwest direction, and a freight branch line of the Union Pacific Railroad traverses the town in an east-northeast to west-southwest direction. Chemung is served by the Harvard post office. Chemung has an area of 0.280 square miles (0.73 km2), all land.
Points of interest
Chemung business district: junction of Route 173 and Oak Grove Road; Dean's Dairy: 6303 Maxon Road; Chemung-Dunham Cemetery: southwest corner of Pagles Road / Sinderson Street.