County outline
Where Coos County is located
Area breakdown
Land accounts for 98% of Coos County’s measured area and water for 2%. Its combined area converts to 4,740.5 square kilometers or approximately 1,171,395 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 1,794.574 | 4,647.925 | 1,148,527.4 |
| Water | 35.73 | 92.54 | 22,867.2 |
| Total | 1,830.304 | 4,740.466 | 1,171,394.6 |
How Coos County compares
By original Census land area, Coos County ranks #1 of 10 in New Hampshire and #330 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 2.267 times the New Hampshire county-equivalent median of 791.6 square miles. It accounts for 20% of the combined county land area in the state.
See the complete New Hampshire ranking · What counts as a county equivalent?
Population and density of Coos County
The Census Bureau estimates that 31,343 people lived in Coos County on July 1, 2025. That ranks #1,448 of 3,222 county equivalents nationally and #10 of 10 in New Hampshire. Since the April 1, 2020 estimates base of 31,269, the population has grown by 74 (+0.2%), compared with +2.7% for New Hampshire as a whole.
With 1,794.6 square miles of land, that is 17 people per square mile (6.7 per km²), placing Coos County #2,397 nationally for density and #10 in New Hampshire. The median county equivalent has 47 people per square mile; the New Hampshire median is 136. Put another way, there are about 37 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 31,235 | 31,402 | 31,444 | 31,247 | 31,377 | 31,343 |
| Change | — | +167 | +42 | −197 | +130 | −34 |
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 Coos County
Coos County is divided into 43 cities and towns. In New Hampshire, county subdivisions are local governments, and together they cover all of the county’s land and residents; a few are unorganized areas without their own government.
The most populous is Berlin city, with 9,502 residents (30.3% of the county). The largest by land is Pittsburg town, at 281.3 mi², or 15.7% of the county’s land. The county seat, Lancaster town, has 3,218 residents. Among those with at least 1,000 residents in 2020, Jefferson town grew fastest since then (+1.8%).
| County subdivision | Population 2025 | Since 2020 | Land mi² | Share of county land |
|---|---|---|---|---|
| Berlin city | 9,502 | +0.8% | 61.3 | 3.4% |
| Lancaster townCounty seat | 3,218 | −0.1% | 50 | 2.8% |
| Gorham town | 2,661 | −1.3% | 31.8 | 1.8% |
| Whitefield town | 2,535 | +1.6% | 34.3 | 1.9% |
| Colebrook town | 2,110 | +1.3% | 40.5 | 2.3% |
| Northumberland town | 2,096 | −1.6% | 35.7 | 2% |
| Milan town | 1,354 | −0.5% | 63.7 | 3.5% |
| Jefferson town | 1,063 | +1.8% | 50 | 2.8% |
| Dalton town | 907 | −2.4% | 27.5 | 1.5% |
| Pittsburg town | 845 | +4.8% | 281.3 | 15.7% |
| Carroll town | 841 | +2.8% | 50.3 | 2.8% |
| Stewartstown town | 774 | −4.1% | 46.3 | 2.6% |
| Columbia town | 673 | +2.3% | 60.8 | 3.4% |
| Stratford town | 646 | −2.4% | 79.2 | 4.4% |
| Stark town | 463 | −2.5% | 58.8 | 3.3% |
Show the other 28 subdivisions
| Name | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Shelburne town | 363 | +2.3% | 47.9 |
| Randolph town | 327 | −0.9% | 47 |
| Dummer town | 313 | +3% | 48 |
| Errol town | 291 | −2.7% | 60.4 |
| Clarksville town | 284 | −2.4% | 60.3 |
| Wentworth location | 29 | −3.3% | 18.3 |
| Millsfield township | 23 | −4.2% | 44.8 |
| Cambridge township | 11 | 0% | 51 |
| Success township | 5 | 0% | 56.5 |
| Dixville township | 4 | 0% | 49 |
| Greens grant | 4 | 0% | 3.667 |
| Thompson and Meserves purchase | 1 | 0% | 18.5 |
| Atkinson and Gilmanton Academy grant | 0 | — | 19.2 |
| Beans grant | 0 | — | 9.661 |
| Beans purchase | 0 | — | 65.2 |
| Chandlers purchase | 0 | — | 2.126 |
| Crawfords purchase | 0 | — | 8.193 |
| Cutts grant | 0 | — | 11.3 |
| Dixs grant | 0 | — | 20 |
| Ervings location | 0 | — | 3.752 |
| Hadleys purchase | 0 | — | 7.407 |
| Kilkenny township | 0 | — | 25.7 |
| Low and Burbanks grant | 0 | — | 26.1 |
| Martins location | 0 | — | 3.725 |
| Odell township | 0 | — | 44.3 |
| Pinkhams grant | 0 | — | 3.793 |
| Sargents purchase | 0 | — | 25.9 |
| Second College grant | 0 | — | 41.3 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Coos County. Land: 2026 Census Gazetteer. How communities are listed.
Metropolitan area
Coos 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 Coos County; 14 of them have most of their land inside the county, and the others mainly cover neighboring areas.
03570035740357503576035790358103582035830358403588035900359203593035950359703598
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 Coos County
Coos County shares a land border with 4 county equivalents, including 2 in Maine and Vermont. It has more land than 3 of them. The largest neighbor is Oxford County (2,077 mi²) and the smallest is Essex County (662.4 mi²). Together with its neighbors, Coos County forms a block of 7,174.4 mi² of land, of which it holds 25%.
| Bordering county equivalent | Land mi² | Size vs. Coos | Compare |
|---|---|---|---|
| Oxford CountyMaine | 2,077 | 1.2× larger | Compare |
| Grafton County | 1,708.6 | 1.1× smaller | Compare |
| Carroll County | 931.9 | 1.9× smaller | Compare |
| Essex CountyVermont | 662.4 | 2.7× smaller | Compare |
How big is Coos County compared with U.S. states?
Coos 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). New Hampshire’s county land could hold about 5 areas the size of Coos County.
Another way to picture it: the same land area would fill a square about 42.4 miles (68.2 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 Coos County?
Coos County has more land than 2,892 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 Coos County at #362 nationally by total area, 32 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 2%, compared with a national county-equivalent median of 1.2% — 0.8 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 Coos County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #329 | Stillwater County, Montana | 1,796.5 | Compare |
| #330 | Coos County, New Hampshire | 1,794.6 | This county |
| #331 | Essex County, New York | 1,794.1 | 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 44.652548, -71.289431. 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: 4,647,924,506 m²; AWATER: 92,541,536 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 Coos County?
Coos County, New Hampshire has 1,794.6 square miles (4,647.9 km²) of land and 35.7 square miles of water, for a total area of 1,830.3 square miles. It ranks #330 of 3,222 U.S. county equivalents by land area.
Is Coos County the largest county in New Hampshire?
Yes. Coos County has the most land of the 10 county equivalents in New Hampshire.
What counties border Coos County?
Coos County shares a land border with Oxford County, Maine, Essex County, Vermont, Carroll County, and Grafton County.
What is the population of Coos County?
The Census Bureau estimates Coos County had 31,343 residents on July 1, 2025, ranking #1,448 of 3,222 county equivalents. That is 17 people per square mile of land.
What is the county seat of Coos County?
The county seat of Coos County is Lancaster.
What cities and towns are in Coos County?
Coos County has 43 county subdivisions (cities, towns and townships). The most populous five are Berlin city, Lancaster town, Gorham town, Whitefield town, and Colebrook town.
Is Coos County part of a metropolitan area?
No. Coos County is outside every metropolitan and micropolitan statistical area in the July 2023 OMB delineation.
How many ZIP codes are in Coos County?
16 ZIP Code Tabulation Areas have land in Coos County, and 14 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Coos 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 Coos County?
The land measurement converts to approximately 1,148,527 acres. Including water, total area is approximately 1,171,395 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.