Salem is a city in and the county seat of Marion County, Illinois, United States. The population was 7,485 at the 2010 census.
Salem is located at 38°38′N 88°57′W / 38.633°N 88.950°W / 38.633; -88.950 (38.6282, -88.9482).
According to the 2010 census, Salem has a total area of 7.097 square miles (18.38 km), of which 6.94 square miles (17.97 km) (or 97.79%) is land and 0.157 square miles (0.41 km) (or 2.21%) is water.
As of the census of 2000, there were 7,909 people, 3,249 households, and 2,082 families residing in the city. The population density was 1,296.5 people per square mile (500.6/km²). There were 3,473 housing units at an average density of 569.3 per square mile (219.8/km²). The racial makeup of the city was 97.13% White, 0.72% African American, 0.30% Native American, 1.15% Asian, 0.04% Pacific Islander, 0.14% from other races, and 0.52% from two or more races. Hispanic or Latino of any race were 0.72% of the population.
There were 3,249 households out of which 28.6% had children under the age of 18 living with them, 48.8% were married couples living together, 11.0% had a female householder with no husband present, and 35.9% were non-families. 32.3% of all households were made up of individuals and 17.2% had someone living alone who was 65 years of age or older. The average household size was 2.32 and the average family size was 2.91.
In the city, the population was spread out with 23.5% under the age of 18, 8.7% from 18 to 24, 26.1% from 25 to 44, 22.1% from 45 to 64, and 19.6% who were 65 years of age or older. The median age was 39 years. For every 100 females, there were 87.6 males. For every 100 females age 18 and over, there were 83.9 males.
The median income for a household in the city was $34,339, and the median income for a family was $42,070. Males had a median income of $31,811 versus $21,931 for females. The per capita income for the city was $16,954. About 6.1% of families and 9.2% of the population were below the poverty line, including 13.2% of those under age 18 and 9.2% of those age 65 or over.