Monticello, IL -- U.S. city in Illinois Population (2000): 5138 Housing Units (2000): 2226 Land area (2000): 2.979123 sq. miles (7.715893 sq. km) Water area (2000): 0.000000 sq. miles (0.000000 sq. km) Total area (2000): 2.979123 sq. miles (7.715893 sq. km) FIPS code: 50244 Located within: Illinois (IL), FIPS 17 Location: 40.028092 N, 88.573003 W ZIP Codes (1990): 61856 Note: some ZIP codes may be omitted esp. for suburbs. Headwords: Monticello, IL Monticello