County outline
Where Cimarron County is located
Area breakdown
Land accounts for 99.7% of Cimarron County’s measured area and water for 0.3%. Its combined area converts to 4,768.1 square kilometers or approximately 1,178,212 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 1,834.808 | 4,752.131 | 1,174,277.1 |
| Water | 6.148 | 15.923 | 3,934.7 |
| Total | 1,840.956 | 4,768.054 | 1,178,211.8 |
How Cimarron County compares
By original Census land area, Cimarron County ranks #4 of 77 in Oklahoma and #320 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 2.286 times the Oklahoma county-equivalent median of 802.7 square miles. It accounts for 2.7% of the combined county land area in the state.
See the complete Oklahoma ranking · What counts as a county equivalent?
Population and density of Cimarron County
The Census Bureau estimates that 2,059 people lived in Cimarron County on July 1, 2025. That ranks #3,115 of 3,222 county equivalents nationally and #77 of 77 in Oklahoma. Since the April 1, 2020 estimates base of 2,290, the population has declined by 231 (−10.1%), compared with +4.1% for Oklahoma as a whole.
With 1,834.8 square miles of land, that is 1.1 people per square mile (0.43 per km²), placing Cimarron County #3,138 nationally for density and #77 in Oklahoma. The median county equivalent has 47 people per square mile; the Oklahoma median is 28. Put another way, there are about 570 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 2,287 | 2,245 | 2,226 | 2,184 | 2,121 | 2,059 |
| Change | — | −42 | −19 | −42 | −63 | −62 |
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 Cimarron County
2 incorporated places lie at least partly in Cimarron County. Together they are home to 1,284 people (62.4%); the other 775 (37.6%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is Boise City city, with 1,040 residents in the county.
| Incorporated place | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Boise City cityCounty seat | 1,040 | −10.6% | 1.476 |
| Keyes town | 244 | −10.3% | 0.361 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Cimarron County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.
Metropolitan area
Cimarron 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 Cimarron County; 4 of them have most of their land inside the county, and the others mainly cover neighboring areas.
7393373937739467394773949
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 Cimarron County
Cimarron County shares a land border with 6 county equivalents, including 5 in Colorado, Texas, New Mexico, and Kansas. It has more land than 3 of them. The largest neighbor is Union County (3,825.1 mi²) and the smallest is Morton County (729.7 mi²). Together with its neighbors, Cimarron County forms a block of 13,412.1 mi² of land, of which it holds 13.7%.
| Bordering county equivalent | Land mi² | Size vs. Cimarron | Compare |
|---|---|---|---|
| Union CountyNew Mexico | 3,825.1 | 2.1× larger | Compare |
| Baca CountyColorado | 2,555 | 1.4× larger | Compare |
| Texas County | 2,041.3 | 1.1× larger | Compare |
| Dallam CountyTexas | 1,503.4 | 1.2× smaller | Compare |
| Sherman CountyTexas | 922.9 | 2× smaller | Compare |
| Morton CountyKansas | 729.7 | 2.5× smaller | Compare |
How big is Cimarron County compared with U.S. states?
Cimarron County has more land than 1 of the 50 states. It is about 1.8 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). Oklahoma’s county land could hold about 37 areas the size of Cimarron County.
Another way to picture it: the same land area would fill a square about 42.8 miles (68.9 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 Cimarron County?
Cimarron County has more land than 2,902 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 Cimarron County at #360 nationally by total area, 40 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% — 0.8 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 Cimarron County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #319 | Logan County, Colorado | 1,838.6 | Compare |
| #320 | Cimarron County, Oklahoma | 1,834.8 | This county |
| #321 | Mountrail County, North Dakota | 1,825.2 | Compare |
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 36.755251, -102.522317. 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: 4,752,131,823 m²; AWATER: 15,923,999 m². Rankings use ALAND; exact ties use ascending GEOID. Tables preserve Census-published square miles to three decimals, with conversions based on those values.
Common questions
How big is Cimarron County?
Cimarron County, Oklahoma has 1,834.8 square miles (4,752.1 km²) of land and 6.148 square miles of water, for a total area of 1,841 square miles. It ranks #320 of 3,222 U.S. county equivalents by land area.
Is Cimarron County the largest county in Oklahoma?
No. Cimarron County ranks #4 of 77 in Oklahoma by land area. The largest is Osage County, with 2,246.7 square miles of land.
What counties border Cimarron County?
Cimarron County shares a land border with Baca County, Colorado, Dallam County, Texas, Union County, New Mexico, Texas County, Sherman County, Texas, and Morton County, Kansas.
What is the population of Cimarron County?
The Census Bureau estimates Cimarron County had 2,059 residents on July 1, 2025, ranking #3,115 of 3,222 county equivalents. That is 1.1 people per square mile of land.
What is the county seat of Cimarron County?
The county seat of Cimarron County is Boise City.
What cities and towns are in Cimarron County?
Cimarron County has 2 incorporated places. The most populous are Boise City city and Keyes town; 775 residents live outside any incorporated place.
Is Cimarron County part of a metropolitan area?
No. Cimarron County is outside every metropolitan and micropolitan statistical area in the July 2023 OMB delineation.
How many ZIP codes are in Cimarron County?
5 ZIP Code Tabulation Areas have land in Cimarron 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 Cimarron 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 Cimarron County?
The land measurement converts to approximately 1,174,277 acres. Including water, total area is approximately 1,178,212 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.