Idaho County area

Population and density of Idaho County

The Census Bureau estimates that 17,874 people lived in Idaho County on July 1, 2025. That ranks #2,004 of 3,222 county equivalents nationally and #20 of 44 in Idaho. Since the April 1, 2020 estimates base of 16,545, the population has grown by 1,329 (+8%), compared with +10.4% for Idaho as a whole.

With 8,477.5 square miles of land, that is 2.1 people per square mile (0.81 per km²), placing Idaho County #3,055 nationally for density and #38 in Idaho. The median county equivalent has 47 people per square mile; the Idaho median is 10. Put another way, there are about 304 acres of land per resident.

U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.

Cities and towns in Idaho County

8 incorporated places lie at least partly in Idaho County. Together they are home to 5,902 people (33%); the other 11,972 (67%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Grangeville city, with 3,621 residents in the county.

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Idaho County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.

Metropolitan area

Idaho County is not part of any metropolitan or micropolitan statistical area in the Office of Management and Budget’s July 2023 delineation; 1,306 other county equivalents are also outside one. These areas are built around an urban core of at least 10,000 people plus the counties tied to it by commuting, so counties outside them are generally rural.

ZIP codes

16 ZIP Code Tabulation Areas have land in Idaho County; 12 of them have most of their land inside the county, and the others mainly cover neighboring areas.

59847835228352583526835308353383536835398354283547835498355283554836118363883654

ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.

Counties bordering Idaho County

Idaho County shares a land border with 9 county equivalents, including 3 in Montana and Oregon. It has more land than every one of them. The largest neighbor is Lemhi County (4,563.7 mi²) and the smallest is Lewis County (478.8 mi²). Together with its neighbors, Idaho County forms a block of 29,979.6 mi² of land, of which it holds 28.3%.

How big is Idaho County compared with U.S. states?

Idaho County has more land than 6 of the 50 states. It is about 1.1 times the land area of Massachusetts (7,801 mi²), while New Hampshire, the next larger state, has 1.1 times as much land (8,954 mi²). Idaho’s county land could hold about 9.7 areas the size of Idaho County.

Another way to picture it: the same land area would fill a square about 92.1 miles (148.2 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.

State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.

What stands out about Idaho County?

Idaho County has more land than 3,190 of the other 3,221 county equivalents in the dataset.

A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.

Does including water change its rank?

Using land plus water places Idaho County at #38 nationally by total area, 6 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.

Its water share is 0.3%, compared with a national county-equivalent median of 1.2% — 0.9 percentage points lower. This describes the statistical geography’s land/water mix, not flood exposure or developable land.

Closest positions in the national land ranking

These entries sit immediately beside Idaho County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.