Plainville is a village in Adams County, Illinois, United States. The population was 264 at the 2010 census. It is part of the Quincy, IL–MO Micropolitan Statistical Area.
Plainville is located at 39°47′4″N 91°11′2″W / 39.78444°N 91.18389°W / 39.78444; -91.18389 (39.784364, -91.183868).
According to the 2010 census, Plainville has a total area of 0.23 square miles (0.60 km), all land.
As of the census of 2000, there were 248 people, 100 households, and 74 families residing in the village. The population density was 1,078.7 people per square mile (416.3/km²). There were 110 housing units at an average density of 478.5 per square mile (184.7/km²). The racial makeup of the village was 99.60% White, and 0.40% from two or more races.
There were 100 households out of which 35.0% had children under the age of 18 living with them, 61.0% were married couples living together, 8.0% had a female householder with no husband present, and 26.0% were non-families. Of all households 22.0% were made up of individuals and 12.0% had someone living alone who was 65 years of age or older. The average household size was 2.48 and the average family size was 2.84.
In the village, the population was spread out with 26.6% under the age of 18, 6.5% from 18 to 24, 30.6% from 25 to 44, 21.4% from 45 to 64, and 14.9% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 89.3 males. For every 100 females age 18 and over, there were 100.0 males.
The median income for a household in the village was $28,438, and the median income for a family was $38,472. Males had a median income of $27,813 versus $21,538 for females. The per capita income for the village was $13,700. About 2.9% of families and 6.9% of the population were below the poverty line, including none of those under the age of eighteen and 17.1% of those sixty five or over.