Market insights · Illinois
St. Clair County, IL: growth, migration and housing
St. Clair County has 250,708 residents, down 2.5% since 2020 (-0.3% in the last year). In 2022–2023, 5,735 households moved in and 6,135 moved out (-400 net), while a net $48.9M of income left. Median household income is $73,854, the median home $180,300 and median rent $1,090 a month.
In Illinois: 64th of 102 counties for 5-year population growth · 49th of 102 counties for net in-migration (per resident) · 29th of 102 counties for median household income · 23rd of 102 counties for median home value.
Where new residents came from
Top counties by households (tax returns) moving to St. Clair County, 2022–2023 (IRS).
| From | Households (tax returns) | Their income (AGI) |
|---|---|---|
| Madison County, IL | 983 | $44.6M |
| St. Louis County, MO | 560 | $28.3M |
| St. Louis city, MO | 411 | $24.2M |
| Monroe County, IL | 168 | $9.7M |
| Clinton County, IL | 146 | $7.7M |
| St. Charles County, MO | 102 | $6.3M |
| Cook County, IL | 87 | $7.9M |
| Jefferson County, MO | 83 | $5.0M |
Where leavers went
Top counties by households leaving St. Clair County, 2022–2023 (IRS).
| To | Households (tax returns) | Their income (AGI) |
|---|---|---|
| Madison County, IL | 1,146 | $59.2M |
| St. Louis County, MO | 626 | $34.6M |
| St. Louis city, MO | 387 | $17.3M |
| Monroe County, IL | 218 | $14.4M |
| Clinton County, IL | 145 | $8.2M |
| Jefferson County, MO | 126 | $7.5M |
| St. Charles County, MO | 121 | $8.4M |
| Randolph County, IL | 94 | $4.8M |
BizyFi in St. Clair County
Fewer than 3 companies in the BizyFi directory are based here. Search them on the company map (company names with a free account), or browse Illinois companies.
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Sources: U.S. Census Bureau population estimates (vintage 2025), American Community Survey 5-year (2024), and IRS Statistics of Income county-to-county migration data (2022–2023). Migration counts are tax returns (roughly households) moving between U.S. counties; the IRS suppresses very small flows. Growth rates, per-1,000 figures, rent share and state ranks are BizyFi calculations. Data updated 2026-10-17. This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.