Clark County area

Clark County, Idaho covers 1,764.1 square miles: 1,763.1 square miles of land and 0.956 square miles of water. Its county seat is Dubois. An estimated 783 people lived there in 2025.

Official Census measurements · GEOID 160332026 Gazetteer · retrieved September 27, 2026
Land area1,763.1 mi²
Water area0.956 mi²
Population (2025)783
People per mi²0.44

County outline

Generalized outline of Clark County, Idaho
2025 Census cartographic boundary, fitted to this frame. County maps are not at a common scale. The 2026 area measurements below come from the separate Gazetteer release. Map source and limitations.

Where Clark County is located

Clark County highlighted on a map of all U.S. county equivalents. About the maps

Area breakdown

Land accounts for 99.9% of Clark County’s measured area and water for 0.1%. Its combined area converts to 4,569 square kilometers or approximately 1,129,025 acres.

Green: land · blue: water

MeasurementSquare milesSquare kilometersAcres
Land1,763.1454,566.5251,128,412.8
Water0.9562.476611.8
Total1,764.1014,569.0011,129,024.6

How Clark County compares

By original Census land area, Clark County ranks #18 of 44 in Idaho and #340 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.

Its land area is 1.34 times the Idaho county-equivalent median of 1,315.7 square miles. It accounts for 2.1% of the combined county land area in the state.

See the complete Idaho ranking · What counts as a county equivalent?

Population and density of Clark County

The Census Bureau estimates that 783 people lived in Clark County on July 1, 2025. That ranks #3,198 of 3,222 county equivalents nationally and #44 of 44 in Idaho. Since the April 1, 2020 estimates base of 788, the population has declined by 5 (−0.6%), compared with +10.4% for Idaho as a whole.

With 1,763.1 square miles of land, that is 0.44 people per square mile (0.17 per km²), placing Clark County #3,200 nationally for density and #44 in Idaho. The median county equivalent has 47 people per square mile; the Idaho median is 10. Put another way, there are about 1,441 acres of land per resident.

Estimated population, 2020–2025 · line scaled to this county’s own range
July 1202020212022202320242025
Estimate791794811798782783
Change—+3+17−13−16+1

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 Clark County

2 incorporated places lie at least partly in Clark County. Together they are home to 545 people (69.6%); the other 238 (30.4%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Dubois city, with 516 residents in the county.

Incorporated placePopulation 2025Since 2020Land mi²
Dubois cityCounty seat516−0.6%2.728
Spencer city290%1.142

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

Metropolitan area

Clark 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

4 ZIP Code Tabulation Areas have land in Clark County; 2 of them have most of their land inside the county, and the others mainly cover neighboring areas.

83423834358344683464

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 Clark County

Clark County shares a land border with 5 county equivalents, including 1 in Montana. It has more land than 1 of them. The largest neighbor is Beaverhead County (5,542.7 mi²) and the smallest is Jefferson County (1,093.7 mi²). Together with its neighbors, Clark County forms a block of 17,063.7 mi² of land, of which it holds 10.3%.

Map of Clark County and the 5 county equivalents that border it Beaverhead County, Montana: 5,542.7 mi² landFremont County, Idaho: 1,864 mi² landButte County, Idaho: 2,236.5 mi² landJefferson County, Idaho: 1,093.7 mi² landLemhi County, Idaho: 4,563.7 mi² land
Clark County (dark) and its bordering county equivalents. Select a neighbor to open its profile. Drawn from the 2025 Census cartographic boundaries in an equal-area projection. How borders are determined.
Bordering county equivalentLand mi²Size vs. ClarkCompare
Beaverhead CountyMontana5,542.73.1× largerCompare
Lemhi County4,563.72.6× largerCompare
Butte County2,236.51.3× largerCompare
Fremont County1,8641.1× largerCompare
Jefferson County1,093.71.6× smallerCompare

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

Clark County has more land than 1 of the 50 states. It is about 1.7 times the land area of Rhode Island (1,033.9 mi²), while Delaware, the next larger state, has 1.1 times as much land (1,948.6 mi²). Idaho’s county land could hold about 47 areas the size of Clark County.

Land area: Clark County and the closest-sized states
Rhode Island1,033.9 mi²
Clark County1,763.1 mi²
Delaware1,948.6 mi²

Another way to picture it: the same land area would fill a square about 42 miles (67.6 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 Clark County?

Clark County has more land than 2,882 of the other 3,221 county equivalents in the dataset.

Land area compared with the typical county equivalent
Clark County1,763.1 mi²
Idaho median1,315.7 mi²
National median604.5 mi²

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 Clark County at #382 nationally by total area, 42 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 0.1%, compared with a national county-equivalent median of 1.2% — 1.1 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 Clark County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Land rankCounty equivalentLand mi²Comparison
#339Caribou County, Idaho1,764.2Compare
#340Clark County, Idaho1,763.1This county
#341Fall River County, South Dakota1,739.9Compare

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.

Representative coordinates

The Census internal point is 44.290218, -112.354613. It represents a location inside the geography; it is not necessarily the centroid or the address of a courthouse.

Source and precision

U.S. Census Bureau, 2026 Gazetteer Files, Counties. Original ALAND: 4,566,524,456 m²; AWATER: 2,476,453 m². Rankings use ALAND; exact ties use ascending GEOID. Tables preserve Census-published square miles to three decimals, with conversions based on those values.

Download the official county source ZIP ↗ · Methodology

Common questions

How big is Clark County?

Clark County, Idaho has 1,763.1 square miles (4,566.5 km²) of land and 0.956 square miles of water, for a total area of 1,764.1 square miles. It ranks #340 of 3,222 U.S. county equivalents by land area.

Is Clark County the largest county in Idaho?

No. Clark County ranks #18 of 44 in Idaho by land area. The largest is Idaho County, with 8,477.5 square miles of land.

What counties border Clark County?

Clark County shares a land border with Beaverhead County, Montana, Fremont County, Butte County, Jefferson County, and Lemhi County.

What is the population of Clark County?

The Census Bureau estimates Clark County had 783 residents on July 1, 2025, ranking #3,198 of 3,222 county equivalents. That is 0.44 people per square mile of land.

What is the county seat of Clark County?

The county seat of Clark County is Dubois.

What cities and towns are in Clark County?

Clark County has 2 incorporated places. The most populous are Dubois city and Spencer city; 238 residents live outside any incorporated place.

Is Clark County part of a metropolitan area?

No. Clark County is outside every metropolitan and micropolitan statistical area in the July 2023 OMB delineation.

How many ZIP codes are in Clark County?

4 ZIP Code Tabulation Areas have land in Clark County, and 2 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.

How does Clark County compare with U.S. states?

It has more land than 1 of the 50 states, including Rhode Island (1,033.9 square miles of land).

How many acres of land are in Clark County?

The land measurement converts to approximately 1,128,413 acres. Including water, total area is approximately 1,129,025 acres. One square mile equals 640 acres.

Why might another source show a different area?

Check whether it reports land or total area, its Census vintage, and its rounding. Our guide explains how to reconcile county area figures.

Can this establish a property boundary?

No. Statistical measurements and generalized maps do not establish property lines. Consult the relevant local surveying or land-records authority.

Cite this county

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