County facts · Population · October 25, 2026
Idaho Population by County, 2025 Census Estimates
Idaho population by county: July 2025 Census estimates for all 44 counties, change since 2020, density, and a link to each official parcel map.
Looking for Idaho population by county? The Census Bureau estimates that Idaho had 2,029,733 residents on July 1, 2025, spread across 44 counties. Ada County is the most populous, with 546,141 people (27% of the state), and Clark County is the least populous, with 783.
The table below lists every county with its 2025 estimate, its April 2020 starting point, the change, people per square mile, and a link to its official parcel viewer.
Idaho population at a glance
- Counties: 44
- Statewide, July 1, 2025: 2,029,733 (April 1, 2020 estimates base: 1,839,123; change +190,610, +10.4%)
- Most populous: Ada County (546,141); least populous: Clark County (783)
- Median county: about 15,048 residents (half of the counties are smaller)
- The 5 largest counties hold 61% of all Idaho residents
- Counties with 1,000,000+ residents: 0 · 100,000+: 4 · under 10,000: 14
- Statewide density: about 25 people per square mile of land
Idaho population by county, July 2025 (all 44)
Percent change runs from the April 1, 2020 estimates base to July 1, 2025. People per square mile is the July 2025 estimate divided by the county's land area in the Census Bureau's 2020 Gazetteer file, so lakes and bays are left out.
How Idaho's population is spread out
Grouping the counties by size shows how concentrated the state is:
| Residents (July 2025) | Counties | Total residents | Share of state |
|---|---|---|---|
| 250,000 to 999,999 | 2 | 821,264 | 40% |
| 100,000 to 249,999 | 2 | 327,635 | 16% |
| 25,000 to 99,999 | 13 | 605,484 | 30% |
| 10,000 to 24,999 | 13 | 198,065 | 10% |
| Under 10,000 | 14 | 77,285 | 4% |
2 counties with at least 250,000 residents hold 40% of the state's population.
Most and least densely populated
The most crowded counties by people per square mile of land:
- Ada County: 519 per sq mi (546,141 people on 1,052 sq mi)
- Canyon County: 469 per sq mi (275,123 people on 587 sq mi)
- Kootenai County: 155 per sq mi (191,864 people on 1,238 sq mi)
- Madison County: 118 per sq mi (55,172 people on 469 sq mi)
- Bannock County: 82 per sq mi (91,591 people on 1,112 sq mi)
The most thinly settled:
- Clark County: 0.4 per sq mi (783 people on 1,763 sq mi)
- Custer County: 0.9 per sq mi (4,636 people on 4,922 sq mi)
- Camas County: 1.2 per sq mi (1,316 people on 1,074 sq mi)
- Butte County: 1.2 per sq mi (2,783 people on 2,236 sq mi)
- Owyhee County: 1.7 per sq mi (12,661 people on 7,668 sq mi)
About these numbers
- They are estimates. Between censuses the Census Bureau's Population Estimates Program updates county totals each year from births, deaths and migration records. The next full count is the 2030 census.
- The base is April 1, 2020. The estimates start from an April 1, 2020 "estimates base" built from the 2020 census, which is why it is slightly different from the published census count.
- Each new release revises the past. A newer vintage can change earlier years as well, so compare numbers from the same release, as this page does.
- Statewide total. The counties add up exactly to the statewide figure of 2,029,733 in the same file.
Using population numbers in a land search
- Big counties, busy offices. In the most populous counties, parcel maps and deed records are usually online and searchable, but recording and permit offices are busier. Allow for that if you are on a deadline.
- Small counties, fewer sales. In counties with only a few thousand people, land changes hands less often, so there are fewer recent sales to compare a price with. Recorded deeds and the local assessor's sales records are the best source.
- Density hints at lot size. A low people-per-square-mile figure usually means farms, ranches and timber tracts; a high one means subdivided lots. The parcel viewer shows the actual parcel lines.
- Check the official map. Use the parcel viewer link in the table for boundaries, parcel numbers and owner names, then confirm anything important with the local assessor and the office that records deeds.
Related guides
- Fastest growing counties in Idaho
- Largest counties in Idaho
- Idaho county GIS websites by viewer
- Idaho landowner maps for hunting
- Most populous counties in the US
- Where people are moving in the US
More: All Idaho counties on Platbookmapper
Sources
- U.S. Census Bureau, Population Estimates Program, county totals, Vintage 2025 (April 1, 2020 estimates base and July 1, 2020–2025 estimates, with components of change). Statewide totals are the sum of the counties and match the file's state row.
- U.S. Census Bureau Gazetteer files, 2020 county land and water area (for people per square mile).
- Platbookmapper county GIS directory (live data file behind our county pages, pulled October 25, 2026) for each official parcel viewer.