The mayor is Don Thiltgen, and the city council is currently composed of Luanne Smith (First Ward), Steve Hasenmiller (Second Ward), Verlyn Scheckel Dawn Marcus (At-Large), (At-Large) and Kurt Ketelsen (At-Large).
De Witt is served by the Union Pacific along the south side.
The gender makeup of the city was 47.4% male and 52.6% female.
The median income for a household in the city was ,720, and the median income for a family was ,063.
The population was 5,322 at the 2010 census, which is a 5.2% increase from the 2000 census, making it the fastest growing city in Clinton County. The racial makeup of the city was 97.1% White, 0.8% African American, 0.1% Native American, 0.4% Asian, 0.2% from other races, and 1.5% from two or more races.
The Milwaukee Road rail between Maquoketa and De Witt were abandoned by 1970. By 1980 both highways were moved to new alignments around the south and west sides of De Witt.
Hispanic or Latino of any race were 1.9% of the population.
There were 2,208 households of which 32.4% had children under the age of 18 living with them, 50.9% were married couples living together, 10.2% had a female householder with no husband present, 3.0% had a male householder with no wife present, and 35.9% were non-families.
31.5% of all households were made up of individuals and 15.9% had someone living alone who was 65 years of age or older.The average household size was 2.37 and the average family size was 2.99. 25.3% of residents were under the age of 18; 7.4% were between the ages of 18 and 24; 24.1% were from 25 to 44; 26% were from 45 to 64; and 17.2% were 65 years of age or older.