Annawan is an incorporated town in Henry County, Illinois, United States. The population was 878 at the 2010 census.
Annawan is located at 41°23′50″N 89°54′32″W / 41.39722°N 89.90889°W / 41.39722; -89.90889 (41.397094, -89.908893).
According to the 2010 census, Annawan has a total area of 1.98 square miles (5.13 km), all land.
As of the census of 2000, there were 868 people, 354 households, and 238 families residing in the village. The population density was 1,273.6 people per square mile (492.8/km²). There were 373 housing units at an average density of 547.3/sq mi (211.8/km²). The racial makeup of the village was 99.88% White, and 0.12% from two or more races. Hispanic or Latino of any race were 1.15% of the population.
There were 354 households out of which 32.8% had children under the age of 18 living with them, 58.5% were married couples living together, 6.5% had a female householder with no husband present, and 32.5% were non-families. 30.5% of all households were made up of individuals and 15.5% had someone living alone who was 65 years of age or older. The average household size was 2.45 and the average family size was 3.07.
In the town, the population was spread out with 27.3% under the age of 18, 6.5% from 18 to 24, 25.1% from 25 to 44, 21.5% from 45 to 64, and 19.6% who were 65 years of age or older. The median age was 39 years. For every 100 females, there were 90.4 males. For every 100 females age 18 and over, there were 86.1 males.
The median income for a household in the town was $38,571, and the median income for a family was $46,563. Males had a median income of $37,237 versus $20,673 for females. The per capita income for the town was $15,839. About 9.0% of families and 9.7% of the population were below the poverty line, including 13.0% of those under age 18 and 2.8% of those age 65 or over.