[3] It was named for Newton Clark, a Dakota Territory legislator in 1873.

[4][5] Clark County terrain consists of rolling hills, dotted with lakes and ponds especially in the east central portion.

[7] As of the 2020 census, there were 3,837 people, 1,361 households, and 853 families residing in the county.

As of the 2010 census, there were 3,691 people, 1,445 households, and 929 families residing in the county.

In terms of ancestry, 52.0% were German, 29.4% were Norwegian, 9.7% were Irish, 7.8% were English, 5.4% were Swedish, and 3.5% were American.