THE ADA COUNTY LAND BRIEF
Land in the
Mountain Home Uplands setting.
Ada County has 1,052.3 square miles of land in Idaho. 5 mapped landscape regions meet across Ada County: Mountain Home Uplands, Treasure Valley, Unwooded Alkaline Foothills, among others.
The Snake River Plain is lower and gentler than its surrounding mountains. Alluvial valleys, sagebrush-covered plains, low hills and scattered lava fields form its principal landscape patterns.
Regional context: Snake River Plain ↗ · Regional mapping across the county footprint
Where the landscape changes
Ada County intersects 5 mapped regional units. The largest mapped shares are:
- Mountain Home Uplands60.6%
- Treasure Valley22.1%
- Unwooded Alkaline Foothills9.8%
- Foothill Shrublands-Grasslands6.9%
- Southern Forested Mountains0.6%
Idaho Batholith in Ada County
A deeply cut mountainous plateau forms the Idaho Batholith. Granitic terrain supports conifer forests, while deep canyons introduce warmer settings with pine, shrubs and grasses.
Read the regional source ↗Finding your parcel within Ada County
The atlas lists 8 cities, towns, townships, and Census communities associated with Ada County, including Boise City, Eagle, Meridian. The list includes overlapping geography types and does not divide the county into exclusive service areas.
Ada County by land and water
The Census records 8.51 square miles of water within Ada County, or 0.8% of its total area. That share is close to Ada County’s 0.8%. This is geographic context; waterfront status and usable land must be checked at the parcel.
For scale, Ada County has 40.3 times the land area of nearby Kuna city (26.1 square miles). These areas describe boundaries, not comparable property prices.
The Census boundary meets Boise County, Canyon County, Elmore County, Gem County, Owyhee County within Idaho. A tract near one of these lines should be matched to the county identifier on its own records.

