Richland County is a county located in the U.S. state of Illinois. According to the 2010 census, it had a population of 16,233. Its county seat is Olney.
According to the U.S. Census Bureau, the county has a total area of 362 square miles (940 km), of which 360 square miles (930 km) is land and 1.9 square miles (4.9 km) (0.5%) is water.
As of the 2010 United States Census, there were 16,233 people, 6,726 households, and 4,438 families residing in the county. The population density was 45.1 inhabitants per square mile (17.4/km). There were 7,513 housing units at an average density of 20.9 per square mile (8.1/km). The racial makeup of the county was 97.3% white, 0.7% Asian, 0.5% black or African American, 0.2% American Indian, 0.4% from other races, and 0.9% from two or more races. Those of Hispanic or Latino origin made up 1.3% of the population. In terms of ancestry, 29.6% were German, 11.7% were American, 11.4% were English, and 9.2% were Irish.
Of the 6,726 households, 28.9% had children under the age of 18 living with them, 51.7% were married couples living together, 9.6% had a female householder with no husband present, 34.0% were non-families, and 29.3% of all households were made up of individuals. The average household size was 2.36 and the average family size was 2.88. The median age was 42.1 years.
The median income for a household in the county was $41,917 and the median income for a family was $53,853. Males had a median income of $41,058 versus $31,296 for females. The per capita income for the county was $22,874. About 9.5% of families and 13.8% of the population were below the poverty line, including 15.1% of those under age 18 and 11.9% of those age 65 or over. Richland is the top ranked most affordable county in Illinois to buy a car and is on average $932 less expensive than other Illinois counties.