Hillsboro is a city in Montgomery County, Illinois, United States. The population was 6,207 at the 2010 census. It is the county seat of Montgomery County.
Hillsboro is located at 39°9′54″N 89°29′4″W / 39.16500°N 89.48444°W / 39.16500; -89.48444 (39.164973, −89.484572).
According to the 2010 census, Hillsboro has a total area of 8.322 square miles (21.55 km), of which 6.55 square miles (16.96 km) (or 78.71%) is land and 1.772 square miles (4.59 km) (or 21.29%) is water.
As of the census of 2000, there were 4,359 people, 1,800 households, and 1,189 families residing in the city. The population density was 1,214.9 people per square mile (468.8/km²). There were 1,944 housing units at an average density of 541.8 per square mile (209.1/km²). The racial makeup of the city was 97.22% White, 1.10% African American, 0.32% Native American, 0.37% Asian, 0.07% Pacific Islander, 0.39% from other races, and 0.53% from two or more races. Hispanic or Latino of any race were 1.19% of the population.
There were 1,800 households out of which 33.1% had children under the age of 18 living with them, 50.2% were married couples living together, 11.9% had a female householder with no husband present, and 33.9% were non-families. 30.0% of all households were made up of individuals and 14.8% had someone living alone who was 65 years of age or older. The average household size was 2.36 and the average family size was 2.91.
In the city, the population was spread out with 25.8% under the age of 18, 8.4% from 18 to 24, 27.2% from 25 to 44, 21.0% from 45 to 64, and 17.6% who were 65 years of age or older. The median age was 38 years. For every 100 females, there were 85.7 males. For every 100 females age 18 and over, there were 80.3 males.
The median income for a household in the city was $33,075, and the median income for a family was $40,135. Males had a median income of $31,821 versus $18,668 for females. The per capita income for the city was $17,458. About 14.3% of families and 17.2% of the population were below the poverty line, including 24.9% of those under age 18 and 11.9% of those age 65 or over.