Harmon County area

Harmon County, Oklahoma covers 538.7 square miles: 537.3 square miles of land and 1.467 square miles of water. Its county seat is Hollis. An estimated 2,327 people lived there in 2025.

Official Census measurements · GEOID 400572026 Gazetteer · retrieved September 27, 2026
Land area537.3 mi²
Water area1.467 mi²
Population (2025)2,327
People per mi²4.3

County outline

Generalized outline of Harmon County, Oklahoma
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 Harmon County is located

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

Area breakdown

Land accounts for 99.7% of Harmon County’s measured area and water for 0.3%. Its combined area converts to 1,395.3 square kilometers or approximately 344,784 acres.

Green: land · blue: water

MeasurementSquare milesSquare kilometersAcres
Land537.2581,391.492343,845.1
Water1.4673.8938.9
Total538.7251,395.291344,784

How Harmon County compares

By original Census land area, Harmon County ranks #71 of 77 in Oklahoma and #1945 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.

Its land area is 0.669 times the Oklahoma county-equivalent median of 802.7 square miles. It accounts for 0.8% of the combined county land area in the state.

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

Population and density of Harmon County

The Census Bureau estimates that 2,327 people lived in Harmon County on July 1, 2025. That ranks #3,093 of 3,222 county equivalents nationally and #76 of 77 in Oklahoma. Since the April 1, 2020 estimates base of 2,490, the population has declined by 163 (−6.5%), compared with +4.1% for Oklahoma as a whole.

With 537.3 square miles of land, that is 4.3 people per square mile (1.7 per km²), placing Harmon County #2,876 nationally for density and #70 in Oklahoma. The median county equivalent has 47 people per square mile; the Oklahoma median is 28. Put another way, there are about 148 acres of land per resident.

Estimated population, 2020–2025 · line scaled to this county’s own range
July 1202020212022202320242025
Estimate2,4762,4002,4252,4062,3352,327
Change—−76+25−19−71−8

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 Harmon County

2 incorporated places lie at least partly in Harmon County. Together they are home to 1,768 people (76%); the other 559 (24%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Hollis city, with 1,673 residents in the county.

Incorporated placePopulation 2025Since 2020Land mi²
Hollis cityCounty seat1,673−6.7%1.485
Gould town95−6.9%0.364

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

Metropolitan area

Harmon 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

6 ZIP Code Tabulation Areas have land in Harmon County; 3 of them have most of their land inside the county, and the others mainly cover neighboring areas.

735327353773544735507355473571

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 Harmon County

Harmon County shares a land border with 6 county equivalents, including 3 in Texas. Each of them has more land than Harmon County. The largest neighbor is Collingsworth County (918.4 mi²) and the smallest is Greer County (639.3 mi²). Together with its neighbors, Harmon County forms a block of 5,190.9 mi² of land, of which it holds 10.3%.

Map of Harmon County and the 6 county equivalents that border it Greer County, Oklahoma: 639.3 mi² landJackson County, Oklahoma: 802.7 mi² landCollingsworth County, Texas: 918.4 mi² landChildress County, Texas: 696.5 mi² landHardeman County, Texas: 695.1 mi² landBeckham County, Oklahoma: 901.7 mi² land
Harmon 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. HarmonCompare
Collingsworth CountyTexas918.41.7× largerCompare
Beckham County901.71.7× largerCompare
Jackson County802.71.5× largerCompare
Childress CountyTexas696.51.3× largerCompare
Hardeman CountyTexas695.11.3× largerCompare
Greer County639.31.2× largerCompare

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

Harmon County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.9 times as much. Oklahoma’s county land could hold about 128 areas the size of Harmon County.

Land area: Harmon County and the closest-sized states
Harmon County537.3 mi²
Rhode Island1,033.9 mi²

Another way to picture it: the same land area would fill a square about 23.2 miles (37.3 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 Harmon County?

Harmon County has more land than 1,277 of the other 3,221 county equivalents in the dataset.

Land area compared with the typical county equivalent
Harmon County537.3 mi²
Oklahoma median802.7 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 Harmon County at #2,047 nationally by total area, 102 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 Harmon County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Land rankCounty equivalentLand mi²Comparison
#1944Sullivan County, New Hampshire537.9Compare
#1945Harmon County, Oklahoma537.3This county
#1946Chittenden County, Vermont536.9Compare

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 34.745971, -99.844194. 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: 1,391,491,970 m²; AWATER: 3,800,410 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 Harmon County?

Harmon County, Oklahoma has 537.3 square miles (1,391.5 km²) of land and 1.467 square miles of water, for a total area of 538.7 square miles. It ranks #1945 of 3,222 U.S. county equivalents by land area.

Is Harmon County the largest county in Oklahoma?

No. Harmon County ranks #71 of 77 in Oklahoma by land area. The largest is Osage County, with 2,246.7 square miles of land.

What counties border Harmon County?

Harmon County shares a land border with Greer County, Jackson County, Collingsworth County, Texas, Childress County, Texas, Hardeman County, Texas, and Beckham County.

What is the population of Harmon County?

The Census Bureau estimates Harmon County had 2,327 residents on July 1, 2025, ranking #3,093 of 3,222 county equivalents. That is 4.3 people per square mile of land.

What is the county seat of Harmon County?

The county seat of Harmon County is Hollis.

What cities and towns are in Harmon County?

Harmon County has 2 incorporated places. The most populous are Hollis city and Gould town; 559 residents live outside any incorporated place.

Is Harmon County part of a metropolitan area?

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

How many ZIP codes are in Harmon County?

6 ZIP Code Tabulation Areas have land in Harmon County, and 3 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.

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

It has less land than every state. Rhode Island, the smallest, has 1.9 times as much land.

How many acres of land are in Harmon County?

The land measurement converts to approximately 343,845 acres. Including water, total area is approximately 344,784 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

Download the complete CSV or JSON dataset