[2] In 2020, the center of population of Wisconsin was located in Green Lake County, near the city of Markesan.

The racial makeup of the county was 92.0% White, 0.6% Black or African American, 0.5% Asian, 0.4% Native American, 0.1% Pacific Islander, 2.1% from other races, and 4.2% from two or more races.

As of the census[11] of 2000, there were 19,105 people, 7,703 households, and 5,322 families residing in the county.

27.00% of all households were made up of individuals, and 13.80% had someone living alone who was 65 years of age or older.

Of these, 77 of the births occurred at home, the fourth highest for Wisconsin counties.

[12] Additionally, there were 11 reported induced abortions performed on women of Green Lake County residence in 2017.