|Elevation||663 ft (202 m)|
|Area||1.46 sq mi (4 km2)|
|- land||1.46 sq mi (4 km2)|
|- water||0.00 sq mi (0 km2)|
|Density||2,349.3/sq mi (907/km2)|
|- summer (DST)||CDT (UTC-5)|
|Wikimedia Commons: Gillespie, Illinois|
Gillespie is located at (39.126023, -89.816403).
According to the 2010 census, Gillespie has a total area of 1.45 square miles (3.76 km2), all land. Gillespie has a large lake, Lake Gillespie, just outside the city limits. Many people from surrounding towns enjoy fishing, boating, water-skiing and sunbathing at Gillespie Lake.
As of the census of 2000, there were 3,412 people, 1,452 households, and 936 families residing in the city. The population density was 2,349.3 people per square mile (908.5/km²). There were 1,547 housing units at an average density of 1,065.1 per square mile (411.9/km²). The racial makeup of the city was 98.56% White, 0.32% African American, 0.21% Native American, 0.12% Asian, 0.06% Pacific Islander, 0.15% from other races, and 0.59% from two or more races. Hispanic or Latino of any race were 0.73% of the population.
There were 1,452 households, of which 28.9% had children under the age of 18 living with them, 50.8% were married couples living together, 9.9% had a female householder with no husband present, and 35.5% were non-families. 31.0% of all households were made up of individuals and 16.4% had someone living alone who was 65 years of age or older. The average household size was 2.35 and the average family size was 2.93.
In the city, the population was spread out with 23.3% under the age of 18, 9.3% from 18 to 24, 27.3% from 25 to 44, 22.7% from 45 to 64, and 17.4% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 88.3 males. For every 100 females age 18 and over, there were 86.1 males.
The median income for a household in the city was $33,168, and the median income for a family was $40,500. Males had a median income of $35,032 versus $23,136 for females. The per capita income for the city was $19,042. About 8.6% of families and 12.4% of the population were below the poverty line, including 17.4% of those under age 18 and 9.5% of those age 65 or over.
- The Annual Black Diamond Days, Gillespie's original festival of coal, is a celebration of coal miners and coal mining which has always been a major business in Macoupin County. The festival is held annually for three days each year on the first weekend in June in Gillespie. Gillespie welcomes visitors in a big way with parades, contests, prizes, a carnival, Mine Rescue Demonstration, 1 Mile Fun Run and 5K Run, arts and crafts, concessions and much more. The 2014 Black Diamond Days Festival will be held on June 6, 7 & 8th.
- Ferras Alqais, singer-songwriter
- W. Russell Arrington, Illinois state legislator and lawyer; born in Gillespie
- Howard Keel, film and television actor and singer
- Harry Patton, pitcher for the St. Louis Cardinals; born in Gillespie
- Raphael Tracey, U.S. soccer player and member of the National Soccer Hall of Fame; born in Gillespie
- Gannett, Henry (1905). The Origin of Certain Place Names in the United States. Govt. Print. Off. p. 137.
- Chicago and North Western Railway Company (1908). A History of the Origin of the Place Names Connected with the Chicago & North Western and Chicago, St. Paul, Minneapolis & Omaha Railways. p. 77.
- "US Gazetteer files: 2010, 2000, and 1990". United States Census Bureau. 2011-02-12. Retrieved 2011-04-23.
- "G001 - Geographic Identifiers - 2010 Census Summary File 1". United States Census Bureau. Retrieved 2015-12-27.
- "Annual Estimates of the Resident Population for Incorporated Places: April 1, 2010 to July 1, 2015". Retrieved July 2, 2016.[permanent dead link]
- "Census of Population and Housing". Census.gov. Archived from the original on May 12, 2015. Retrieved June 4, 2015.
- "American FactFinder". United States Census Bureau. Archived from the original on 2013-09-11. Retrieved 2008-01-31.