|Area||1.6 sq mi (4 km2)|
|- land||1.6 sq mi (4 km2)|
|Density||1,537/sq mi (593/km2)|
|- summer (DST)||CDT (UTC-5)|
|Area code||815, 779|
|Wikimedia Commons: Fairmont, Illinois|
Fairmont is located at (41.562673, -88.062305).
According to the United States Census Bureau, the CDP has a total area of 1.6 square miles (4.1 km2), all land.
At the 2000 census, there were 2,563 people, 861 households and 626 families residing in the CDP. The population density was 1,555.6 per square mile (599.7/km²). There were 901 housing units at an average density of 546.9/sq mi (210.8/km²). The racial makeup of the CDP was 36.17% White, 53.61% African American, 0.23% Native American, 0.47% Asian, 0.04% Pacific Islander, 6.32% from other races, and 3.16% from two or more races. Hispanic or Latino of any race were 10.89% of the population.
There were 861 households of which 30.0% had children under the age of 18 living with them, 43.2% were married couples living together, 20.4% had a female householder with no husband present, and 27.2% were non-families. 21.8% of all households were made up of individuals and 7.2% had someone living alone who was 65 years of age or older. The average household size was 2.97 and the average family size was 3.48.
Age distribution was 27.6% under the age of 18, 11.0% from 18 to 24, 28.1% from 25 to 44, 21.2% from 45 to 64, and 12.1% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 103.1 males. For every 100 females age 18 and over, there were 102.4 males.
The median household income was $40,907, and the median family income was $47,257. Males had a median income of $28,438 versus $26,696 for females. The per capita income for the CDP was $17,260. About 7.5% of families and 14.0% of the population were below the poverty line, including 22.3% of those under age 18 and 7.6% of those age 65 or over.