Sullivan is a city located in Moultrie County Illinois. It is also the county seat of Moultrie County. With a 2020 population of 4,371, it is the 354th largest city in Illinois and the 5157th largest city in the United States . Sullivan is currently declining at a rate of -0.70% annually and its population has decreased by -1.55% since the most recent census, which recorded a population of 4,440 in 2010. Sullivan reached it's highest population of 4,526 in 1980. Spanning over 3 miles, Sullivan has a population density of 1,579 people per square mile.
The average household income in Sullivan is $61,319 with a poverty rate of 12.23%. The median rental costs in recent years comes to $715 per month, and the median house value is $92,500. The median age in Sullivan is 37.6 years, 34 years for males, and 42.2 years for females.