| Historical population of|
As of the census of 2000, there were 17,328 people, 7,385 households, and 4,645 families residing in the town. The population density was 1,776.0 people per square mile (685.5/km²). There were 7,707 housing units at an average density of 789.9/sq mi (304.9/km²). The racial makeup of the town was 93.52% White, 2.25% African American, 0.17% Native American, 1.67% Asian, 0.01% Pacific Islander, 1.19% from other races, and 1.19% from two or more races. Hispanic or Latino of any race were 3.57% of the population.
There were 7,385 households out of which 26.3% had children under the age of 18 living with them, 49.4% were married couples living together, 10.0% had a female householder with no husband present, and 37.1% were non-families. 31.5% of all households were made up of individuals and 10.4% had someone living alone who was 65 years of age or older. The average household size was 2.32 and the average family size was 2.93.
In the town the population was spread out with 21.2% under the age of 18, 6.7% from 18 to 24, 32.0% from 25 to 44, 24.8% from 45 to 64, and 15.2% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 95.4 males. For every 100 females age 18 and over, there were 93.1 males.
The median income for a household in the town was $48,136, and the median income for a family was $60,586. Males had a median income of $41,541 versus $31,281 for females. The per capita income for the town was $23,257. About 4.2% of families and 5.1% of the population were below the poverty line, including 4.2% of those under age 18 and 5.5% of those age 65 or over.
There is one middle school serving grades 6-8, the Middle School of Plainville. The middle school adopts the same mascot and colors as the town high school, with the exception that they are sometimes known as the "Li'l Blue Devils."
Plainville High School is the town high school. The school mascot is the Blue Devil and the colors are blue and white, same as nearby Central Connecticut State University.