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St. Clair County, Illinois

St. Clair County, Illinois
Downtown Belleville Illinois Courthouse.jpg
St. Clair County Courthouse, Belleville
Flag of St. Clair County, Illinois
Flag
Map of Illinois highlighting St. Clair County
Location in the U.S. state of Illinois
Map of the United States highlighting Illinois
Illinois's location in the U.S.
Founded 1790
Named for Arthur St. Clair
Seat Belleville
Largest city Belleville
Area
 • Total 674 sq mi (1,746 km2)
 • Land 658 sq mi (1,704 km2)
 • Water 16 sq mi (41 km2), 2.4%
Population
 • (2010) 270,056
 • Density 411/sq mi (159/km²)
Congressional district 12th
Time zone Central: UTC-6/-5
Website www.co.st-clair.il.us
Belleville, Illinois
Climate chart ()
J F M A M J J A S O N D
 
 
2
 
 
40
22
 
 
2.2
 
 
46
27
 
 
3.5
 
 
57
35
 
 
3.9
 
 
68
45
 
 
4.2
 
 
77
54
 
 
4
 
 
86
63
 
 
3.5
 
 
90
67
 
 
3.3
 
 
88
64
 
 
3
 
 
82
56
 
 
2.9
 
 
71
45
 
 
3.9
 
 
56
36
 
 
3
 
 
44
27
Average max. and min. temperatures in °F
Precipitation totals in inches
Source: The Weather Channel
J F M A M J J A S O N D
 
 
2
 
 
40
22
 
 
2.2
 
 
46
27
 
 
3.5
 
 
57
35
 
 
3.9
 
 
68
45
 
 
4.2
 
 
77
54
 
 
4
 
 
86
63
 
 
3.5
 
 
90
67
 
 
3.3
 
 
88
64
 
 
3
 
 
82
56
 
 
2.9
 
 
71
45
 
 
3.9
 
 
56
36
 
 
3
 
 
44
27
Average max. and min. temperatures in °F
Precipitation totals in inches
Source: The Weather Channel