Louisville is a village in Clay County, Illinois, United States, along the Little Wabash River. The population was 1,139 at the 2010 census. It is the county seat of Clay County.
Louisville is located near the center of Clay County at 38°46′17″N 88°30′23″W / 38.77139°N 88.50639°W / 38.77139; -88.50639 (38.771356, -88.506301). U.S. Route 45 passes through the village, leading north 25 miles (40 km) to Effingham and south 8 miles (13 km) to Flora.
According to the 2010 census, Louisville has a total area of 0.75 square miles (1.94 km), all land. The Little Wabash River flows past the east side of the village.
As of the census of 2000, there were 1,242 people, 503 households, and 311 families residing in the village. The population density was 1,794.1 people per square mile (695.0/km²). There were 543 housing units at an average density of 784.4 per square mile (303.8/km²). The racial makeup of the village was 99.28% White, 0.16% African American, 0.16% Native American, 0.08% Asian, 0.24% from other races, and 0.08% from two or more races. Hispanic or Latino of any race were 0.40% of the population.
There were 503 households out of which 28.4% had children under the age of 18 living with them, 48.7% were married couples living together, 9.7% had a female householder with no husband present, and 38.0% were non-families. 34.4% of all households were made up of individuals and 20.1% had someone living alone who was 65 years of age or older. The average household size was 2.31 and the average family size was 2.97.
In the village, the age distribution of the population shows 23.7% under the age of 18, 8.5% from 18 to 24, 24.5% from 25 to 44, 21.9% from 45 to 64, and 21.4% who were 65 years of age or older. The median age was 39 years. For every 100 females, there were 92.3 males. For every 100 females age 18 and over, there were 84.8 males.
The median income for a household in the village was $25,250, and the median income for a family was $35,673. Males had a median income of $27,083 versus $21,719 for females. The per capita income for the village was $13,119. About 13.1% of families and 18.9% of the population were below the poverty line, including 19.7% of those under age 18 and 15.6% of those age 65 or over.