County facts · Land area · October 22, 2026
Largest Counties in Idaho by Area and Population
The largest Idaho counties by land area and by 2023 population, plus the smallest, county seats and a link to each official parcel map.
Looking for the largest counties in Idaho? Idaho has 44 counties covering about 82,645 square miles of land, based on the Census Bureau's 2020 Gazetteer. The largest by land area is Idaho County, at about 8,477 square miles, roughly 21 times the size of the smallest, Payette County (407 sq mi). Measured by people instead, the largest is Ada County, with about 524,673 residents in the Census Bureau's July 1, 2023 estimate.
The tables below rank the counties both ways. Each row links to the county's Platbookmapper page and straight to its official parcel viewer.
Idaho counties at a glance
- Counties: 44
- Land area: about 82,645 sq mi, plus about 923 sq mi of water inside county lines
- Residents, 2023 estimates: about 1,964,726, or about 24 people per square mile of land
- Median county land area: about 1,316 sq mi
- With a verified public parcel viewer in our directory: 43 of 44 (13 of them through a statewide viewer)
The 10 largest Idaho counties by land area
| # | County | Seat | Land (sq mi) | 2023 pop. | People per sq mi | Parcel viewer |
|---|---|---|---|---|---|---|
| 1 | Idaho County | Grangeville | 8,477 | 17,890 | 2.1 | ArcGIS Web AppBuilder |
| 2 | Owyhee County | Murphy | 7,668 | 12,722 | 1.7 | ArcGIS Experience Builder |
| 3 | Custer County | Challis | 4,922 | 4,523 | 0.9 | Idaho statewide Parcels layer in ArcGIS Map Viewer |
| 4 | Lemhi County | Salmon | 4,564 | 8,441 | 1.8 | ArcGIS Experience Builder |
| 5 | Valley County | Cascade | 3,665 | 12,644 | 3.4 | Idaho statewide Parcels layer in ArcGIS Map Viewer |
| 6 | Elmore County | Mountain Home | 3,075 | 29,724 | 9.7 | ArcGIS Experience Builder |
| 7 | Blaine County | Hailey | 2,638 | 25,041 | 9.5 | Idaho statewide Parcels layer in ArcGIS Map Viewer |
| 8 | Shoshone County | Wallace | 2,637 | 14,026 | 5.3 | ArcGIS Experience Builder |
| 9 | Cassia County | Burley | 2,566 | 25,696 | 10 | ArcGIS Experience Builder |
| 10 | Clearwater County | Orofino | 2,457 | 9,214 | 3.7 | Idaho statewide Parcels layer in ArcGIS Map Viewer |
Together these 10 cover about 52% of Idaho's land area and hold about 8% of its residents.
The 10 most populous Idaho counties
| # | County | Seat | 2023 pop. | Land (sq mi) | Parcel viewer |
|---|---|---|---|---|---|
| 1 | Ada County | Boise | 524,673 | 1,052 | listed link under review |
| 2 | Canyon County | Caldwell | 257,674 | 587 | ArcGIS Web AppBuilder |
| 3 | Kootenai County | Coeur d'Alene | 185,010 | 1,238 | county web map |
| 4 | Bonneville County | Idaho Falls | 131,366 | 1,866 | ArcGIS Experience Builder |
| 5 | Twin Falls County | Twin Falls | 95,156 | 1,922 | ArcGIS Experience Builder |
| 6 | Bannock County | Pocatello | 90,400 | 1,112 | ArcGIS Experience Builder |
| 7 | Madison County | Rexburg | 54,547 | 469 | county web map |
| 8 | Bonner County | Sandpoint | 52,547 | 1,733 | county web map |
| 9 | Bingham County | Blackfoot | 50,395 | 2,094 | Idaho statewide Parcels layer in ArcGIS Map Viewer |
| 10 | Nez Perce County | Lewiston | 42,987 | 848 | Idaho statewide Parcels layer in ArcGIS Map Viewer |
These 10 hold about 76% of Idaho's residents in the 2023 estimates.
The 5 smallest Idaho counties by land area
| County | Seat | Land (sq mi) | 2023 pop. | Parcel viewer |
|---|---|---|---|---|
| Payette County | Payette | 407 | 27,279 | ArcGIS Experience Builder |
| Teton County | Driggs | 449 | 12,549 | Idaho statewide Parcels layer in ArcGIS Map Viewer |
| Madison County | Rexburg | 469 | 54,547 | county web map |
| Lewis County | Nezperce | 479 | 3,739 | ArcGIS Experience Builder |
| Gem County | Emmett | 560 | 21,071 | ArcGIS Experience Builder |
Most and least crowded
- Most people per square mile: Ada County, about 499 (then Canyon County, 439, and Kootenai County, 149)
- Fewest people per square mile: Clark County, about 0.5 (then Custer County, 0.9, and Camas County, 1.1)
Counties with the most water
The Census Bureau reports water separately from land. It counts lakes, reservoirs, rivers and, along a coast or a Great Lake, the water inside the boundary.
- Bonner County: about 185 sq mi of water, 10% of its total area
- Bear Lake County: about 74 sq mi of water, 7% of its total area
- Kootenai County: about 71 sq mi of water, 5% of its total area
Using these numbers in a land search
- Land area is not parcel count. A large rural county can hold fewer parcels than a small suburban one, so size alone says little about how busy its parcel map is.
- Search, don't scroll. In a big county, type an address, owner name or parcel number into the viewer's search box, where it has one, instead of panning across the map.
- Records follow the county line. Deeds, plats and tax bills are kept by the county where the parcel sits, so a tract that crosses a county line usually has a parcel number on each side.
- Rounded figures. Land and water areas are rounded to whole square miles (one decimal for very small places). People per square mile is the 2023 estimate divided by land area.
Related guides
- Idaho county GIS websites by viewer
- Idaho landowner maps for hunting
- Idaho–Montana border counties
- Largest county in each state
- Largest counties in the US by land area
More: All Idaho counties on Platbookmapper
Sources
- U.S. Census Bureau Gazetteer files, 2020 county land and water area.
- U.S. Census Bureau, Population Estimates Program, county totals, Vintage 2023 (July 1, 2023 estimates)
- Platbookmapper county GIS directory (live data file behind our county pages, pulled October 22, 2026) for each official parcel viewer.
- County seats: Wikidata (county seat property), cross-checked against Census place names.