Sullivan is a city in Moultrie County, Illinois, United States. The population was 4,440 at the 2010 census. It is the county seat and largest city of Moultrie County. Sullivan is named after Sullivan’s Island, South Carolina, where Fort Moultrie is located.
Sullivan is located at 39°35′54″N 88°36′36″W / 39.59833°N 88.61000°W / 39.59833; -88.61000 (39.598270, -88.610038).
According to the 2010 census, the city has a total area of 2.68 square miles (6.9 km), all land.
As of the census of 2000, there were 4,326 people, 1,820 households, and 1,188 families residing in the city. The population density was 2,121.5 people per square mile (818.8/km²). There were 1,945 housing units at an average density of 953.8 per square mile (368.1/km²). The racial makeup of the city was 98.68% White, 0.30% African American, 0.12% Native American, 0.16% Asian, 0.09% from other races, and 0.65% from two or more races. Hispanic or Latino of any race were 0.39% of the population.
There were 1,820 households out of which 28.3% had children under the age of 18 living with them, 51.8% were married couples living together, 10.4% had a female householder with no husband present, and 34.7% were non-families. 31.0% of all households were made up of individuals and 16.5% had someone living alone who was 65 years of age or older. The average household size was 2.28 and the average family size was 2.84.
In the city the population was spread out with 22.8% under the age of 18, 8.3% from 18 to 24, 25.9% from 25 to 44, 21.3% from 45 to 64, and 21.7% who were 65 years of age or older. The median age was 40 years. For every 100 females, there were 84.4 males. For every 100 females age 18 and over, there were 81.2 males.
The median income for a household in the city was $33,197, and the median income for a family was $41,894. Males had a median income of $31,754 versus $20,631 for females. The per capita income for the city was $17,693. About 5.4% of families and 8.8% of the population were below the poverty line, including 9.3% of those under age 18 and 8.9% of those age 65 or over.