Andover is a village in Henry County, Illinois, United States. The population was 578 at the 2010 census, down from 594 in 2000.
Andover is located at 41°17′42″N 90°17′26″W / 41.29500°N 90.29056°W / 41.29500; -90.29056 (41.295011, -90.290658).
According to the 2010 census, Andover has a total area of 0.99 square miles (2.56 km), all land.
As of the census of 2000, there were 594 people, 220 households, and 174 families residing in the village. The population density was 594.8 people per square mile (229.3/km²). There were 226 housing units at an average density of 226.3 per square mile (87.3/km²). The racial makeup of the village was 98.48% White, 0.17% Native American, 0.84% Asian, and 0.51% from two or more races. Hispanic or Latino of any race were 0.84% of the population. 27.8% were of Swedish, 26.8% German, 10.2% Irish, 7.7% English and 5.7% American ancestry according to Census 2000.
There were 220 households out of which 34.5% had children under the age of 18 living with them, 70.9% were married couples living together, 6.4% had a female householder with no husband present, and 20.5% were non-families. 16.8% of all households were made up of individuals and 8.2% had someone living alone who was 65 years of age or older. The average household size was 2.70 and the average family size was 3.06.
In the village, the population was spread out with 26.1% under the age of 18, 7.1% from 18 to 24, 26.1% from 25 to 44, 27.9% from 45 to 64, and 12.8% who were 65 years of age or older. The median age was 40 years. For every 100 females, there were 96.0 males. For every 100 females age 18 and over, there were 97.7 males.
The median income for a household in the village was $46,944, and the median income for a family was $49,821. Males had a median income of $40,000 versus $26,625 for females. The per capita income for the village was $18,439. About 4.1% of families and 5.9% of the population were below the poverty line, including 7.1% of those under age 18 and 17.8% of those age 65 or over.