[3] The county takes its name from the French word for "open level country".

It was formed from parts of Greene and Franklin counties by legislative action.

[6] As of the census[12] of 2000, there were 38,890 people, 14,952 households, and 10,870 families living in the county.

The racial makeup of the county was 95.73% White, 2.30% Black or African American, 0.31% Native American, 0.25% Asian, 0.02% Pacific Islander, 0.31% from other races, and 1.08% from two or more races.

There were 14,952 households, out of which 34.00% had children under the age of 18 living with them, 59.70% were married couples living together, 9.20% had a female householder with no husband present, and 27.30% were non-families.

23.50% of all households were made up of individuals, and 9.40% had someone living alone who was 65 years of age or older.

As of the 2010 United States Census, there were 40,097 people, 15,329 households, and 10,925 families living in the county.

[14] The racial makeup of the county was 94.7% white, 2.2% black or African American, 0.4% Asian, 0.4% American Indian, 0.4% from other races, and 1.9% from two or more races.

[13] In terms of ancestry, 27.6% were German, 14.9% were Irish, 14.3% were American, and 11.8% were English.

The following libraries serve the communities of Champaign County.