Williamson County, Illinois demographics
Williamson County, Illinois (county FIPS 17199) has a median household income of $65,604 (±$3,466) and a total population of 66,876 in the American Community Survey 5-year estimates for 2020-2024.
Margins of error are at the 90% confidence level. The figures describe 2020-2024 (dollars in 2024 dollars), not the present. 22 ZIP Code Tabulation Areas overlap the county (Census 2020).
Data as of Oct 22, 2026 (Olympus publication) · Markdown version
- Values are ACS 5-year estimates for 2020-2024 (dollars in 2024 dollars), not current figures.
- ZCTA-county overlaps come from the Census 2020 relationship file and use 2020 counties, by land area; Connecticut uses its legacy counties, not the planning regions in ACS 2022+.
ACS 5-year estimates, 2020-2024
Census American Community Survey 5-year estimates for 2020-2024, with 90% margins of error as published by the Census Bureau.
| Metric | Estimate | Margin of error (90%) | ACS table |
|---|---|---|---|
| Total population | 66,876 | none (controlled estimate) | B01003 |
| Median age | 41.6 years | ±0.3 years | B01002 |
| Households | 28,983 | ±394 | B11001 |
| Median household income (inflation-adjusted to the final ACS year) | $65,604 | ±$3,466 | B19013 |
| Median value of owner-occupied housing units | $156,400 | ±$5,461 | B25077 |
| Median gross rent | $930 | ±$37 | B25064 |
| Owner-occupied share of occupied housing units | 70.7% | none (derived from several estimates) | B25003 (derived) |
| Renter-occupied share of occupied housing units | 29.4% | none (derived from several estimates) | B25003 (derived) |
| High school graduate or higher (age 25+) | 92.8% | none (derived from several estimates) | B15003 (derived) |
| Bachelor's degree or higher (age 25+) | 26.3% | none (derived from several estimates) | B15003 (derived) |
| Share of people below the poverty level | 13.8% | none (derived from several estimates) | B17001 (derived) |
| Unemployment rate (civilian labor force) | 5% | none (derived from several estimates) | B23025 (derived) |
- Dollar values are in 2024 inflation-adjusted dollars.
- Percentages' margins of error are in percentage points (pp).
Geography
| Measure | Value |
|---|---|
| County FIPS | 17199 |
| Land area | 420.21 sq mi |
| Water area | 24.12 sq mi |
| Population density | 159 per sq mi of land |
| Geography vintage | 2024 Gazetteer |
ZIP codes (ZCTAs) in this county
ZCTAs that overlap the county in the Census 2020 ZCTA to county relationship file, largest share of the county's land first.
| ZCTA | Share of county land | Share of ZCTA land | County is the ZCTA's primary county |
|---|---|---|---|
| 62959 | 34% | 100% | Yes |
| 62922 | 11.1% | 73.5% | Yes |
| 62902 | 9.7% | 63.6% | Yes |
| 62918 | 8.9% | 99.9% | Yes |
| 62951 | 6.6% | 100% | Yes |
| 62974 | 6.2% | 100% | Yes |
| 62890 | 5.7% | 23.2% | |
| 62948 | 4.8% | 100% | Yes |
| 62987 | 3.9% | 17.9% | |
| 62958 | 2.7% | 23% | |
| 62917 | 1.5% | 21.6% | |
| 62896 | 1.3% | 9.1% | |
| 62924 | 1.1% | 12.2% | |
| 62901 | 0.7% | 10.7% | |
| 62933 | 0.6% | 100% | Yes |
| 62939 | 0.4% | 4% | |
| 62949 | 0.4% | 100% | Yes |
| 62921 | 0.1% | 100% | Yes |
| 62935 | 0.1% | 0.8% | |
| 62915 | 0.1% | 100% | Yes |
| 62841 | 0.1% | 100% | Yes |
| 62967 | 0.1% | 3.6% |
Sources
- American Community Survey 5-year estimates (Census Data API) — U.S. Census Bureau. ACS 5-year 2020-2024 (release acs5-2024:county), source date 2025-09-02. https://api.census.gov/data/2024/acs/acs5?get=NAME,B01003_001E,B01003_001M,B01002_001E,B01002_001M,B11001_001E,B11001_001M,B19013_001E,B19013_001M,B25077_001E,B25077_001M,B25064_001E,B25064_001M,B25003_001E,B25003_002E,B25003_003E,B15003_001E,B15003_017E,B15003_018E,B15003_019E,B15003_020E,B15003_021E,B15003_022E,B15003_023E,B15003_024E,B15003_025E,B17001_001E,B17001_002E,B23025_003E,B23025_005E&for=county:199&in=state:17
- Published by Olympus on Oct 22, 2026.
- Source data: U.S. Census Bureau. Works of the U.S. government are not subject to copyright in the United States.
- This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.
Get this data from the API
The same figures, with provenance on every value, from the API (free API key, reference) or from an AI agent through the Olympus MCP server.
curl -s "https://api.olympus.new-odyssey.com/v1/geo-demographics/counties/17199" -H "X-API-Key: $OLYMPUS_API_KEY"get_us_demographics {"county_fips":"17199"}