Sullivan is a city in Hamilton Township, Sullivan County, Indiana, United States. The population was 4,249 at the 2010 census. It is part of the Terre Haute Metropolitan Statistical Area. The city is the county seat of Sullivan County. History The Sullivan post office has been in operation since 1843. Geography Sullivan is located at (39.096888, -87.406447). According to the 2010 census, Sullivan has a total area of , all land. Demographics 2010 census As of the census of 2010, there were 4,249 people, 1,835 households, and 1,073 families living in the city. The population density was . There were 2,110 housing units at an average density of . The racial makeup of the city was 97.7% White, 0.1% African American, 0.4% Native American, 0.2% Asian, 0.4% from other races, and 1.2% from two or more races. Hispanic or Latino of any race were 1.4% of the population. There were 1,835 households, of which 29.4% had children under the age of 18 living with them, 39.2% were married couples living together, 14.3% had a female householder with no husband present, 5.0% had a male householder with no wife present, and 41.5% were non-families. 37.1% of all households were made up of individuals, and 18.1% had someone living alone who was 65 years of age or older. The average household size was 2.27 and the average family size was 2.96. The median age in the city was 39.8 years. 23.8% of residents were under the age of 18; 9.3% were between the ages of 18 and 24; 23.4% were from 25 to 44; 25% were from 45 to 64; and 18.5% were 65 years of age or older. The gender makeup of the city was 46.3% male and 53.7% female. 2000 census As of the census of 2000, there were 4,617 people, 1,958 households, and 1,176 families living in the city. The population density was . There were 2,264 housing units at an average density of . The racial makeup of the city was 97.92% White, 0.50% African American, 0.37% Native American, 0.24% Asian, 0.13% from other races, and 0.84% from two or more races. Hispanic or Latino of any race were 0.82% of the population. There were 1,958 households, out of which 28.5% had children under the age of 18 living with them, 45.0% were married couples living together, 11.6% had a female householder with no husband present, and 39.9%