Valley County area

Valley County, Idaho covers 3,733.5 square miles: 3,665.1 square miles of land and 68.4 square miles of water. Its county seat is Cascade. An estimated 12,831 people lived there in 2025.

Official Census measurements · GEOID 160852026 Gazetteer · retrieved September 27, 2026
Land area3,665.1 mi²
Water area68.4 mi²
Population (2025)12,831
People per mi²3.5

County outline

Generalized outline of Valley 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 Valley County is located

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

Area breakdown

Land accounts for 98.2% of Valley County’s measured area and water for 1.8%. Its combined area converts to 9,669.7 square kilometers or approximately 2,389,442 acres.

Green: land · blue: water

MeasurementSquare milesSquare kilometersAcres
Land3,665.129,492.6172,345,676.8
Water68.383177.11143,765.1
Total3,733.5039,669.7282,389,441.9

How Valley County compares

By original Census land area, Valley County ranks #5 of 44 in Idaho and #138 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.

Its land area is 2.786 times the Idaho county-equivalent median of 1,315.7 square miles. It accounts for 4.4% of the combined county land area in the state.

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

Population and density of Valley County

The Census Bureau estimates that 12,831 people lived in Valley County on July 1, 2025. That ranks #2,299 of 3,222 county equivalents nationally and #27 of 44 in Idaho. Since the April 1, 2020 estimates base of 11,743, the population has grown by 1,088 (+9.3%), compared with +10.4% for Idaho as a whole.

With 3,665.1 square miles of land, that is 3.5 people per square mile (1.4 per km²), placing Valley County #2,944 nationally for density and #37 in Idaho. The median county equivalent has 47 people per square mile; the Idaho median is 10. Put another way, there are about 183 acres of land per resident.

Estimated population, 2020–2025 · line scaled to this county’s own range
July 1202020212022202320242025
Estimate11,84112,25212,43212,65812,81712,831
Change—+411+180+226+159+14

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 Valley County

3 incorporated places lie at least partly in Valley County. Together they are home to 5,406 people (42.1%); the other 7,425 (57.9%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is McCall city, with 4,133 residents in the county. The county seat, Cascade city, has 1,018 residents.

Incorporated placePopulation 2025Since 2020Land mi²
McCall city4,133+12.4%9.055
Cascade cityCounty seat1,018+2.1%4.124
Donnelly city255+1.6%0.714

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

Metropolitan area

Valley 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

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

8361183615836388365783677

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 Valley County

Valley County shares a land border with 6 county equivalents. It has more land than 3 of them. The largest neighbor is Idaho County (8,477.5 mi²) and the smallest is Gem County (559.8 mi²). Together with its neighbors, Valley County forms a block of 25,450.4 mi² of land, of which it holds 14.4%.

Map of Valley County and the 6 county equivalents that border it Idaho County, Idaho: 8,477.5 mi² landBoise County, Idaho: 1,899.4 mi² landCuster County, Idaho: 4,922.2 mi² landAdams County, Idaho: 1,362.8 mi² landLemhi County, Idaho: 4,563.7 mi² landGem County, Idaho: 559.8 mi² land
Valley 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. ValleyCompare
Idaho County8,477.52.3× largerCompare
Custer County4,922.21.3× largerCompare
Lemhi County4,563.71.2× largerCompare
Boise County1,899.41.9× smallerCompare
Adams County1,362.82.7× smallerCompare
Gem County559.86.5× smallerCompare

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

Valley County has more land than 2 of the 50 states. It is about 1.9 times the land area of Delaware (1,948.6 mi²), while Connecticut, the next larger state, has 1.3 times as much land (4,842.5 mi²). Idaho’s county land could hold about 23 areas the size of Valley County.

Land area: Valley County and the closest-sized states
Delaware1,948.6 mi²
Valley County3,665.1 mi²
Connecticut4,842.5 mi²

Another way to picture it: the same land area would fill a square about 60.5 miles (97.4 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 Valley County?

Valley County has more land than 3,084 of the other 3,221 county equivalents in the dataset.

Land area compared with the typical county equivalent
Valley County3,665.1 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 Valley County at #146 nationally by total area, 8 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 1.8%, compared with a national county-equivalent median of 1.2% — 0.7 percentage points higher. 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 Valley County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Land rankCounty equivalentLand mi²Comparison
#137Grand County, Utah3,672.9Compare
#138Valley County, Idaho3,665.1This county
#139Lincoln County, Montana3,612.6Compare

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 44.855976, -115.618026. 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: 9,492,617,026 m²; AWATER: 177,110,439 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 Valley County?

Valley County, Idaho has 3,665.1 square miles (9,492.6 km²) of land and 68.4 square miles of water, for a total area of 3,733.5 square miles. It ranks #138 of 3,222 U.S. county equivalents by land area.

Is Valley County the largest county in Idaho?

No. Valley County ranks #5 of 44 in Idaho by land area. The largest is Idaho County, with 8,477.5 square miles of land.

What counties border Valley County?

Valley County shares a land border with Idaho County, Boise County, Custer County, Adams County, Lemhi County, and Gem County.

What is the population of Valley County?

The Census Bureau estimates Valley County had 12,831 residents on July 1, 2025, ranking #2,299 of 3,222 county equivalents. That is 3.5 people per square mile of land.

What is the county seat of Valley County?

The county seat of Valley County is Cascade.

What cities and towns are in Valley County?

Valley County has 3 incorporated places. The most populous are McCall city, Cascade city, and Donnelly city; 7,425 residents live outside any incorporated place.

Is Valley County part of a metropolitan area?

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

How many ZIP codes are in Valley County?

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

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

It has more land than 2 of the 50 states, including Delaware (1,948.6 square miles of land).

How many acres of land are in Valley County?

The land measurement converts to approximately 2,345,677 acres. Including water, total area is approximately 2,389,442 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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