Gillespie, IL -- U.S. city in Illinois Population (2000): 3412 Housing Units (2000): 1547 Land area (2000): 1.452378 sq. miles (3.761642 sq. km) Water area (2000): 0.000000 sq. miles (0.000000 sq. km) Total area (2000): 1.452378 sq. miles (3.761642 sq. km) FIPS code: 29236 Located within: Illinois (IL), FIPS 17 Location: 39.126023 N, 89.816403 W ZIP Codes (1990): Note: some ZIP codes may be omitted esp. for suburbs. Headwords: Gillespie, IL Gillespie