Petersburg is a city located in Menard County Illinois. It is also the county seat of Menard County. With a 2020 population of 2,184, it is the 463rd largest city in Illinois and the 7296th largest city in the United States . Petersburg is currently declining at a rate of -0.68% annually and its population has decreased by -3.36% since the most recent census, which recorded a population of 2,260 in 2010. Petersburg reached it's highest population of 2,332 in 2011. Spanning over 2 miles, Petersburg has a population density of 1,398 people per square mile.
The average household income in Petersburg is $66,023 with a poverty rate of 20.30%. The median rental costs in recent years comes to $681 per month, and the median house value is $98,000. The median age in Petersburg is 40.5 years, 40.3 years for males, and 40.7 years for females.