|Area||2.1 sq mi (5 km2)|
|Density||1,753.8 / sq mi (677 / km2)|
|- summer (DST)||EDT (UTC-5)|
Thompsonville is located at (40.281373, -80.119665).
According to the United States Census Bureau, the CDP has a total area of 2.1 square miles (5.4 km2), of which, 2.0 square miles (5.2 km2) of it is land and 0.04 square miles (0.10 km2) of it (1.44%) is water.
As of the census of 2000, there were 3,592 people, 1,228 households, and 1,024 families residing in the CDP. The population density was 1,753.8 people per square mile (676.5/km²). There were 1,254 housing units at an average density of 612.3/sq mi (236.2/km²). The racial makeup of the CDP was 98.13% White, 0.33% African American, 0.06% Native American, 0.81% Asian, 0.28% from other races, and 0.39% from two or more races. Hispanic or Latino of any race were 0.70% of the population.
There were 1,228 households out of which 34.7% had children under the age of 18 living with them, 76.8% were married couples living together, 4.3% had a female householder with no husband present, and 16.6% were non-families. 14.7% of all households were made up of individuals and 7.6% had someone living alone who was 65 years of age or older. The average household size was 2.73 and the average family size was 3.03.
In the CDP the population was spread out with 24.3% under the age of 18, 4.0% from 18 to 24, 20.7% from 25 to 44, 29.0% from 45 to 64, and 22.0% who were 65 years of age or older. The median age was 46 years. For every 100 females there were 88.5 males. For every 100 females age 18 and over, there were 84.6 males.
The median income for a household in the CDP was $75,000, and the median income for a family was $89,587. Males had a median income of $70,240 versus $38,839 for females. The per capita income for the CDP was $36,853. About 2.5% of families and 3.9% of the population were below the poverty line, including 2.2% of those under age 18 and 3.9% of those age 65 or over.