Columbia is a city mainly in Monroe County with a small portion in St. Clair County in the U.S. state of Illinois, about south of St. Louis, Missouri. The population was 10,999 at the 2020 census. History Columbia was first incorporated in 1859 as a small farming settlement, but had been occupied by various Native American cultures for 12,000 years. The earliest group encountered by European settlers were members of what became the Illinois Confederation, though they had moved to the area from the Great Lakes region only a few centuries before. Geography Columbia is located at (38.449172, -90.208500). According to the 2010 census, Columbia has a total area of , of which (or 99.37%) is land and (or 0.63%) is water. Columbia is bounded on the west by the Mississippi River. Running in a diagonal line just northeast of Columbia is the border of St. Clair County, beyond which lies Dupo to the north and Millstadt to the east. To the south is Waterloo. Waterloo and Columbia are expected to grow right up to the borders of the other, in effect extending St. Louis's urban sprawl from South St. Louis County across the Jefferson Barracks Bridge into the heart of the formerly rural Monroe County. Demographics As of the census of 2010, there were 9,707 people. 3,792 households and 2,692 families reside in the city. The population density was 932.5 people per square mile. There were 3,977 housing units at an average density of 382 per square mile. The racial makeup of the city was 97.4% White, 0.4% African American, 0.1% Native American, 0.7% Asian, 0.6% from other races, and 0.9% from two or more races. Hispanic or Latino of any race were 2% of the population. There were 3,792 households, out of which 32.9% had children under the age of 18 living with them, 59.1% were married couples living together, 8.6% had a female householder with no husband present, and 29.0% were non-families. 24.2% of all households were made up of individuals, and 10.9% had someone living alone who was 65 years of age or older. The average household size was 2.53 and the average family size was 3.03. In the city, the age distribution of the population shows 25.0% under the age of 18, 5.3% from 20 to 24, 25.6% from 25 to 44, 27.9% from 45 to 64, and 14.3% who were 65 years of age