Menard County is a county in the U.S. state of Illinois. According to the 2010 United States Census, it had a population of 12,705. Its county seat is Petersburg, which is also the location of the county’s only stop light.
According to the US Census Bureau, the county has an area of 315 square miles (820 km), of which 314 square miles (810 km) is land and 1.0 square mile (2.6 km) (0.3%) is water.
As of the 2010 United States Census, there were 12,705 people, 5,140 households, and 3,683 families residing in the county. The population density was 40.4 inhabitants per square mile (15.6/km). There were 5,654 housing units at an average density of 18.0 per square mile (6.9/km). The racial makeup of the county was 97.5% white, 0.6% black or African American, 0.3% American Indian, 0.2% Asian, 0.4% from other races, and 1.1% from two or more races. Those of Hispanic or Latino origin made up 1.0% of the population. In terms of ancestry, 32.5% were German, 20.8% were American, 15.6% were Irish, and 14.3% were English.
Of the 5,140 households, 32.4% had children under the age of 18 living with them, 57.5% were married couples living together, 9.6% had a female householder with no husband present, 28.3% were non-families, and 24.3% of all households were made up of individuals. The average household size was 2.44 and the average family size was 2.87. The median age was 42.6 years.
The median income for a household in the county was $56,230 and the median income for a family was $65,882. Males had a median income of $42,408 versus $36,735 for females. The per capita income for the county was $26,281. About 6.1% of families and 7.7% of the population were below the poverty line, including 10.4% of those under age 18 and 9.4% of those age 65 or over.