Williamson County GIS Maps
Williamson County, Illinois, has 67,153 residents and covers 420.2 square miles. The population grew 1.2% between the 2010 and 2020 census. More residents moved in than left over that decade. The FIPS code for Williamson County is 17199.
Marion is the county's largest population center. Williamson County also includes 12 zip codes, 9 public school districts and 29 municipalities. Those boundaries help explain why population, schools, and housing can look different from one part of the county to another. The map below shows how those county lines, zip codes, and school districts fit together, and the sections that follow use that same geography to show population, demographics, school enrollment and housing patterns in more detail.
Maps, GIS layers and sample data. Paid packages add full layers, analytics and database files.
Williamson County Trends
- Population
- 67,153▴
- Median Home Value
- $145,600▴
- K-12 Enrollment
- 12,482▾
County analytics dashboards with historical trends & projections included in package downloads.
Free starter access previews county maps, lightweight GIS, and sample data. Paid packages unlock full GIS layers, analytics, and database files.
Williamson County Maps
The maps below show a few of the county map styles included in our downloads. County packages include map exports in JPEG, PNG, SVG, PDF and GeoTIFF formats plus more than 20 GIS layers for mapping, research and analysis. Available layers include zip codes, area codes, subdivisions, school districts, political boundaries, roads, water features, points of interest and more.
County packages also include historical county demographics, business intelligence, analytical dashboards, AI-ready prompts, markdown files and related reference data. Everything is organized to save hours of manual work collecting current data, cleaning it and joining it together. That makes it easier to move faster on analytics, due diligence, business planning and location research. Paid packages are built for commercial use, but some package contents include source-specific attribution or notice guidance. Review Licensing & Data Source Notices.
Williamson County Population
Williamson County had 67,153 residents in 2020. That was 1.2% higher than in 2010. Williamson County added 5,857 people between 2000 and 2020, which points to steady long-term growth. The county is fairly spread out, with about 160 people per square mile. Some of the county's most populated postal areas include Marion, Herrin and Carterville.
Population Trend in Williamson County IL
Williamson County Population per 2000, 2010 and 2020 census counts with a baseline 2030 projection.
Williamson County Zip Codes
Williamson County has 12 zip codes. Some of the county's most populated zip codes include Marion (62959), Herrin (62948) and Carterville (62918). Marion is the largest zip by population, with about 27,629 residents or 41% of the county total. Together, the three largest zips account for about 76% of all county residents based on 2020 population estimates.
Most Populated Zip Codes in Williamson County IL
| ZIP | Area | Population | Trend |
|---|---|---|---|
| 62959 | Marion | 27,629 | ▴ 2.5% |
| 62948 | Herrin | 12,536 | ▾ -2.6% |
| 62918 | Carterville | 10,538 | ▴ 7.6% |
| 62951 | Johnston City | 5,136 | ▾ -4% |
| 62902 | Carbondale | 4,344 | ▾ -4.1% |
| Download all zip code data | |||
Williamson County Zip Code populations and trends per most recent census data.
Williamson County Demographics
Williamson County has a median age of 41.4, which makes the county a little older than Illinois overall. About 21.5% of residents are under 18, while 19.6% are 65 or older. That gives the county a fairly even mix of younger families and older adults. The largest age group is 25 to 44 at about 32.3% of the population, which points to a solid working-age base. About 27.5% of adults have a bachelor's degree or higher, above the statewide figure of 37.2%. The county is mostly White by population, though Hispanic, Asian, Black and multiracial residents are also part of the local mix.
Key Demographics for Williamson County IL
Median Age
41.4
Under 18
21.5%
Age 65+
19.6%
Bachelor's+
27.5%
Williamson County School Districts
Williamson County is served by 9 public school districts with 12,482 students enrolled in 2024. The largest districts on the county map are Marion Community Unit 2, Herrin Community Unit 4 and Carterville Community Unit 5. Those three districts account for about 65% of public school enrollment in the map area. Total enrollment has stayed fairly steady in recent years, but it is slightly lower than it was in 2017.
Largest School Districts by Enrollment in Williamson County IL
| District | Enrollment | Share | Trend |
|---|---|---|---|
| Marion Community Unit School District 2 | 3,684 | 29.5% | ▴ 1.2% |
| Herrin Community Unit School District 4 | 2,320 | 18.6% | ▾ -1.6% |
| Carterville Community Unit School District 5 | 2,162 | 17.3% | ▾ -0.2% |
| Frankfort Community Unit School District 168 | 1,517 | 12.2% | ▾ -0.5% |
| Johnston City Community Unit School District 1 | 1,057 | 8.5% | ▾ -0.8% |
| Download all school district data | |||
Williamson County school district enrollment and trends per most recent NCES reporting data.
Williamson County Housing & Real Estate
Williamson County has a median home value of $145,600 and a median gross rent of $897. About 71% of occupied homes in the county are owner-occupied, so the local housing market leans heavily toward ownership. Home values run below the Illinois median, while rents come in below the state average. In March 2026, the median listing price was $194,923 and homes spent about 53 days on the market.
Williamson County Housing Mix
Williamson County housing mix: owner, renter and vacant units.
Williamson County Housing Trends
Williamson County median home value and rent trend (last 5 years).
Businesses in Williamson County, IL
Williamson County has 3,199 business listings across 576 categories. The largest categories in Williamson County business listings are Churches & Religious Organizations (120, 3.8%), Real Estate Agents (51, 1.6%), and Auto Repair (51, 1.6%). The full Williamson County business listings dataset includes names, categories, addresses and contact details where available. Williamson County packages also include U.S. Census County Business Patterns data with establishment counts, employment and payroll by industry sector.
Top Business Categories in Williamson County, IL
| Category | Businesses | Share |
|---|---|---|
| Churches & Religious Organizations | 120 | 3.8% |
| Real Estate Agents | 51 | 1.6% |
| Auto Repair | 51 | 1.6% |
| Medical Center | 49 | 1.5% |
| Community & Nonprofits | 47 | 1.5% |
| Contractors | 43 | 1.3% |
| Insurance Agencies | 43 | 1.3% |
| Medical Offices | 42 | 1.3% |
| Banks & Credit Unions | 38 | 1.2% |
| Beauty Salons | 36 | 1.1% |
Williamson County Business Listings
| Business | Category | City |
|---|---|---|
| ARCH - Active Recovery Center | Abuse And Addiction Treatment | Energy |
| Snows Unlimited | Accommodation | Marion |
| Kemper CPA Group LLP | Accountant | Marion |
| MarionGoofy Golf | Active Life | Marion |
| Lion's Den | Adult Entertainment | Marion |
| Bow Tie Interactive | Advertising Agency | Carterville |
| Southern FS | Agricultural Service | Marion |
| Veterans Airport of Southern Illinois | Airport | Marion |
| K. D. Crain & Sons, Inc. | Altering And Remodeling Contractor | Johnston City |
| Air Evac Lifeteam | Ambulance And Ems Services | Marion |
| Download Williamson County business listings | ||
Williamson County business listings sourced from Overture Maps. Includes locations with a high level of confidence.
Williamson County Basemaps
Williamson County map and data packages include a set of useful basemaps to help you get started quickly. These include a custom light grey canvas, USGS topo, imagery and other reference layers that make it easier to build clear, meaningful county maps using the included GIS layers, your own data or both. Pre-rendered map tiles for the light grey basemap are included so you can use them offline or host them on your own CDN.
Get the Full Williamson County Data Package
This page shows a preview of what's included in the Williamson County data package. The full package gives you a ready-to-use county data system with GIS layers, historical data, maps, database files and planning tools that save hours of manual data gathering, cleanup and joins. Everything is organized to help you skip data wrangling and start analysis faster.
- 20+ GIS layers for zip codes, school districts, roads, water, boundaries and more
- Historical county demographics, housing, income and trend data
- ZIP code population files and school district enrollment history
- Database files, markdowns, AI-ready prompts and documentation
- Map exports in PNG, JPEG, PDF, SVG and GeoTIFF formats
- Offline-ready data explorer, map and analytics tools
Paid packages support commercial use, client work, and derived outputs. Some package contents may include source-specific attribution or provider notices. See Licensing & Data Source Notices.
One-time · instant download · 30-day refund guarantee · See full package details
Preview a Live Package Demo
See exactly what is included in a county data package. Inspect how files are organized, the interactive data explorer and how maps and analytics are laid out. The demo loads a real sample package from Illinois — explore the full structure before you buy.
No email or download required. Opens in a preview window on this page.
Nearby Counties
Browse county data pages for the counties that border Williamson County. These nearby pages include the same mix of county maps, demographic summaries, school district context, housing trends and package links.