Petersburg
- County:
- Menard County
- County Seat:
- Yes
- Area (mi²):
- 1.562
- State:
- Illinois
Petersburg is a city located in Menard County, Illinois. Petersburg has a 2026 population of 2,156. It is also the county seat of Menard County. Petersburg is currently declining at a rate of -0.28% annually and its population has decreased by -2.84% since the most recent census, which recorded a population of 2,219 in 2020.
The median household income in Petersburg is $56,458 with a poverty rate of 15.7%. The median age in Petersburg is 38.7 years: 33.1 years for males, and 42.2 years for females. For every 100 females there are 89.4 males.