Market insights · Illinois
Williamson County, IL: growth, migration and housing
Williamson County has 67,225 residents, up 0.1% since 2020 (+0.2% in the last year). In 2022–2023, 1,618 households moved in and 1,513 moved out (+105 net), while a net $10.5M of income left. Median household income is $65,604, the median home $156,400 and median rent $930 a month.
In Illinois: 17th of 102 counties for 5-year population growth · 6th of 102 counties for net in-migration (per resident) · 61st of 102 counties for median household income · 34th of 102 counties for median home value.
Where new residents came from
Top counties by households (tax returns) moving to Williamson County, 2022–2023 (IRS).
| From | Households (tax returns) | Their income (AGI) |
|---|---|---|
| Jackson County, IL | 277 | $12.9M |
| Franklin County, IL | 258 | $11.5M |
| Saline County, IL | 97 | $5.1M |
| Johnson County, IL | 72 | $4.2M |
| Jefferson County, IL | 40 | $1.6M |
| Union County, IL | 40 | $3.1M |
| Cook County, IL | 28 | $1.2M |
| Perry County, IL | 26 | $1.4M |
Where leavers went
Top counties by households leaving Williamson County, 2022–2023 (IRS).
| To | Households (tax returns) | Their income (AGI) |
|---|---|---|
| Jackson County, IL | 239 | $10.1M |
| Franklin County, IL | 212 | $9.8M |
| Saline County, IL | 74 | $3.4M |
| Johnson County, IL | 67 | $4.5M |
| St. Clair County, IL | 39 | $2.3M |
| Jefferson County, IL | 31 | $1.6M |
| St. Louis County, MO | 30 | $1.7M |
| Union County, IL | 29 | $2.1M |
BizyFi in Williamson County
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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.