Illinois · FIPS 17125 · County seat: Havana
Mason County, IL GIS & Parcel Viewer
Use this page to reach the official county parcel map for Mason County, Illinois. The button below opens Mason Co, Illinois Map in a new tab, so you can look up parcels by address, owner or parcel number on the source site itself.
Open the Mason County parcel map ↗
Opens masonil.wthgis.com in a new tab. We link out and never embed or copy parcel data.
Quick facts
| Official map | Mason Co, Illinois Map |
|---|---|
| Type | County-run map |
| Website | masonil.wthgis.com |
| Access | Free, no login (checked Oct 2026) |
| County seat | Havana |
| Population | 12,523 (2023 Census Bureau estimate) |
| Land area | 539 sq mi |
| FIPS code | 17125 |
Who runs this map
Mason County runs this viewer (directly or through a contracted vendor), which makes it the closest thing to the source for local parcel lines. When we tested the link in October 2026 it opened with no login and no fee.
Finding a property on this map
- Press the button above. This county's viewer runs on WTH GIS; 44 counties in our directory use the same service.
- Find the search option and look up a property, or zoom in on the map.
- Click a lot to see its details.
- Check the toolbar for layers, measuring and printing.
Many parcel sites expect owner names last name first. If a full name finds nothing, try just the surname.
Mason County by the numbers
Census Bureau figures put Mason County at about 12,523 people (2023 estimate) on roughly 539 square miles of land, which is about 23 residents per square mile. By population it ranks 82nd of 102 counties in Illinois. The county seat is Havana.
Neighboring counties
Mason County shares a border with the counties below. Each link has its own official map:
Before you rely on the lines
Online parcel lines are drawn for tax and planning use. They can be off by several feet, so use a recorded plat or a licensed surveyor for fences, setbacks or a sale.