Petersburg is a city in and the county seat of Menard County, Illinois, United States, on the bluffs and part of the floodplain overlooking the Sangamon River. It is part of the Springfield, Illinois Metropolitan Statistical Area. The population was 2,258 at the 2020 census, nearly unchanged from 2010. Petersburg is located approximately 2 miles (3 km) north of New Salem, the original location where Abraham Lincoln first settled, as he started his career.

Illinois Route 97 (IL 97) is a north–south state highway in the central and western portions of the U.S. state of Illinois. It extends from I-55 Business in Springfield northwest to U.S. Highway 150 (US 150) near Galesburg. It crosses over the Illinois River on a bridge west of Havana. This is a distance of 102.23 miles (164.52 km).