The county was named in honor of the seventh Governor of New York State, DeWitt Clinton.

[3] DeWitt County is included in Bloomington–Normal, IL Metropolitan Statistical Area.

[5] As of the 2010 United States census, there were 16,561 people, 6,811 households, and 4,618 families residing in the county.

There were 7,521 housing units at an average density of 18.9 per square mile (7.3/km2).

[12] In terms of ancestry, 31.2% were American, 21.7% were German, 15.8% were English, and 12.3% were Irish.