Richland County is a county located in the U.S. state of Illinois. According to the 2020 United States census, it had a population of 15,813.^[1] Its county seat is Olney.^{[2][3]: County Seats}

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Richland County
County
Richland County Courthouse in Olney
Location within the U.S. state of Illinois
Illinois's location within the U.S.
Coordinates: 38°43′N 88°05′W
Country	United States
State	Illinois
Founded	February 24, 1841
Named for	Richland County, Ohio
Seat	Olney
Largest city	Olney
Area
• Total	362 sq mi (940 km2)
• Land	356 sq mi (920 km2)
• Water	1.9 sq mi (5 km2)  0.5%
Population  (2020)
• Total	15,813
• Estimate  (2021)	15,796
• Density	44/sq mi (17/km2)
Time zone	UTC−6 (Central)
• Summer (DST)	UTC−5 (CDT)
Congressional district	12th

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Richland County was established in 1841 out of portions of East part of Clay and West part of Lawrence counties.^[4] It was named for Richland County, Ohio, where many of the early settlers migrated from.^{[3]: Origin of the name of the county}

• Richland County at the time of its creation in 1841

According to the U.S. Census Bureau, the county has a total area of 362 square miles (940 km²), of which 360 square miles (930 km²) is land^{[5]: Population tab, Population Density sub-tab} and 1.9 square miles (4.9 km²) (0.5%) is water.^[6]

As of the 2010 United States Census, there were 16,233 people, 6,726 households, and 4,438 families residing in the county.^[14] By 2020, the population had decreased to 15,813 people.^{[5]: Population tab, Population Density sub-tab} The 2010 population density was 45.1 inhabitants per square mile (17.4/km²), which decreased to 43.1 inhabitants per square mile (16.6/km²) in the 2020 census.^{[5]: Population tab, Population Density sub-tab} In 2010, there were 7,513 housing units, compared to 7,364 in 2020,^{[5]: Housing tab, Occupied Units sub-tab} at an average density of 20.9 per square mile (8.1/km²).^[6] The 2010 racial makeup of the county was 97.3% white (94.2%, 2020), 0.7% Asian (0.8%, 2020), 0.5% black or African American (same, 2020), 0.2% American Indian (same, 2020), 0.4% (0.5%, 2020) from other races, and 0.9% from two or more races (3.7%, 2020).^{[5]: for 2020—Race alone tab, all sub-tabs} Those of Hispanic or Latino origin made up 1.3% (1.7%, 2020) of the population.^{[5]: Hispanic Origin tab, Hispanic or Latino sub-tab [14]} In terms of ancestry, 29.6% were German, 11.7% were American, 11.4% were English, and 9.2% were Irish.^[15]

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.^[14]

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.^[16] 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.^[17]

• Alexander W. Swanitz (1851–1915), civil engineer who participated in the construction of railroads in various parts of the country
• Dial D. Ryder (1938–2011), gun smith

• National Register of Historic Places listings in Richland County