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St. Clair County, IL Demographics

St. Clair County, IL is the 9th most populous of 102 counties in Illinois, with 257,400 residents across 658 square miles. That is about 391 people per square mile.

At the 2020 census

Population 257,400
Land area 658 sq mi
Density 391 / sq mi

Data: 2020 Census · American Community Survey 2024

How St. Clair County compares to the US

We're computing this county's comparison table — check back shortly. Population, land area, and density above are already exact.

Central Location: St. Clair County, IL

Measured from the county's main population center using 2020 census blocks.

We're computing the drive-time and radius areas around St. Clair County, IL — check back shortly. Meanwhile you can drop a pin anywhere in the radius tool.

Census tracts in St. Clair County, IL

Name Population Sq mi Per sq mi
Census Tract 5034.04 7,971 12.6 632
Census Tract 5033.22 7,555 3.8 1,978
Census Tract 5033.04 6,759 9.4 723
Census Tract 5032.03 6,756 46.8 145
Census Tract 5039.08 6,429 14.4 446
Census Tract 5033.23 6,399 4.6 1,388
Census Tract 5043.54 6,321 2.0 3,135
Census Tract 5033.34 6,153 2.4 2,610
Census Tract 5033.24 6,109 1.8 3,440
Census Tract 5034.12 6,082 7.4 824
Census Tract 5034.14 5,969 3.6 1,665
Census Tract 5034.13 5,683 2.1 2,676
Census Tract 5040.02 5,511 135.9 41
Census Tract 5032.02 5,461 25.1 217
Census Tract 5039.07 5,444 6.3 868
Census Tract 5043.55 5,300 3.8 1,411
Census Tract 5039.06 5,295 46.1 115
Census Tract 5023 5,205 7.2 727
Census Tract 5040.01 5,184 69.5 75
Census Tract 5033.32 5,109 2.2 2,300
Census Tract 5016.02 4,980 1.2 3,993
Census Tract 5026.02 4,809 2.5 1,916
Census Tract 5031.02 4,653 11.3 412
Census Tract 5043.56 4,519 3.0 1,484
Census Tract 5043.57 4,408 25.4 174
Census Tract 5043.53 4,362 7.7 568
Census Tract 5016.04 4,323 1.3 3,319
Census Tract 5043.52 4,203 2.8 1,483
Census Tract 5032.11 4,146 3.8 1,097
Census Tract 5043.59 4,137 32.7 127
Census Tract 5043.58 3,883 32.6 119
Census Tract 5039.03 3,853 27.3 141
Census Tract 5034.16 3,767 3.5 1,076
Census Tract 5024.04 3,702 9.6 386
Census Tract 5016.06 3,605 1.2 3,037
Census Tract 5033.01 3,588 1.4 2,479
Census Tract 5043.51 3,529 1.2 2,949
Census Tract 5034.11 3,419 2.9 1,163
Census Tract 5019 3,269 0.7 4,495
Census Tract 5017 3,185 1.1 3,018
Census Tract 5034.15 3,079 3.5 881
Census Tract 5018.01 3,045 0.7 4,352
Census Tract 5039.05 2,996 4.7 637
Census Tract 5026.03 2,915 5.9 498
Census Tract 5012 2,626 1.6 1,684
Census Tract 5015.02 2,613 1.3 1,973
Census Tract 5013 2,568 1.8 1,440
Census Tract 5016.05 2,535 0.7 3,386
Census Tract 5031.01 2,525 22.8 111
Census Tract 5009 2,485 1.2 2,129
Census Tract 5018.02 2,481 0.6 3,818
Census Tract 5016.07 2,332 1.5 1,550
Census Tract 5045.01 2,329 2.0 1,187
Census Tract 5021 2,246 4.4 509
Census Tract 5014 2,167 0.8 2,745
Census Tract 5028 2,155 1.8 1,214
Census Tract 5046 1,765 1.2 1,465
Census Tract 5029 1,634 3.4 481
Census Tract 5015.01 1,565 1.5 1,035
Census Tract 5005 1,464 0.6 2,279
Census Tract 5045.02 1,301 5.1 253
Census Tract 5038 1,280 3.9 326
Census Tract 5011 1,216 0.9 1,403
Census Tract 5022 1,171 1.6 751
Census Tract 5004 1,046 1.1 914
Census Tract 5025 1,004 1.6 637
Census Tract 5027 975 0.7 1,307
Census Tract 5024.01 832 0.8 1,087

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About this page

This page shows demographics for a US county from the 2020 census and the American Community Survey: population, land area, density, urban share, and how the county compares to national averages for income, housing, age, and more.

Counties subdivide into census tracts, listed below with their populations. The drive-time and radius tables measure the population around the county's main population center.

Read how BlockAtlas computes population within an area →