County outline
Where Merrimack County is located
Area breakdown
Land accounts for 97.7% of Merrimack County’s measured area and water for 2.3%. Its combined area converts to 2,473.4 square kilometers or approximately 611,184 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 932.851 | 2,416.073 | 597,024.6 |
| Water | 22.124 | 57.301 | 14,159.4 |
| Total | 954.975 | 2,473.374 | 611,184 |
How Merrimack County compares
By original Census land area, Merrimack County ranks #3 of 10 in New Hampshire and #768 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 1.178 times the New Hampshire county-equivalent median of 791.6 square miles. It accounts for 10.4% 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 Merrimack County
The Census Bureau estimates that 158,078 people lived in Merrimack County on July 1, 2025. That ranks #447 of 3,222 county equivalents nationally and #3 of 10 in New Hampshire. Since the April 1, 2020 estimates base of 153,816, the population has grown by 4,262 (+2.8%), compared with +2.7% for New Hampshire as a whole.
With 932.9 square miles of land, that is 169 people per square mile (65 per km²), placing Merrimack County #709 nationally for density and #4 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 3.8 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 154,061 | 154,660 | 156,220 | 156,883 | 157,547 | 158,078 |
| Change | — | +599 | +1,560 | +663 | +664 | +531 |
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 Merrimack County
Merrimack County is divided into 27 cities and towns. In New Hampshire, county subdivisions are local governments, and together they cover all of the county’s land and residents.
The most populous is Concord city, with 44,597 residents (28.2% of the county), and it is also the largest by land at 63.9 mi². Among those with at least 1,000 residents in 2020, Dunbarton town grew fastest since then (+7.7%).
| County subdivision | Population 2025 | Since 2020 | Land mi² | Share of county land |
|---|---|---|---|---|
| Concord cityCounty seat | 44,597 | +1.4% | 63.9 | 6.9% |
| Hooksett town | 15,346 | +3.3% | 36 | 3.9% |
| Franklin city | 8,839 | +1.1% | 27.4 | 2.9% |
| Bow town | 8,415 | +2.2% | 28.2 | 3% |
| Pembroke town | 7,579 | +5.2% | 22.6 | 2.4% |
| Henniker town | 6,256 | +1.1% | 44.1 | 4.7% |
| Hopkinton town | 6,120 | +3.5% | 43.3 | 4.6% |
| Loudon town | 5,781 | +3.5% | 46.2 | 4.9% |
| Northfield town | 5,081 | +4.4% | 28.5 | 3.1% |
| Epsom town | 5,057 | +4.6% | 34.4 | 3.7% |
| Allenstown town | 4,882 | +3.7% | 20.5 | 2.2% |
| New London town | 4,411 | +0.2% | 22.3 | 2.4% |
| Boscawen town | 4,255 | +6.4% | 24.9 | 2.7% |
| Pittsfield town | 4,148 | +1.8% | 24 | 2.6% |
| Dunbarton town | 3,233 | +7.7% | 30.9 | 3.3% |
Show the other 12 subdivisions
| Name | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Warner town | 2,902 | −0.9% | 55.2 |
| Chichester town | 2,834 | +6.3% | 21.2 |
| Canterbury town | 2,463 | +3.4% | 43.9 |
| Andover town | 2,456 | +2.3% | 40.1 |
| Newbury town | 2,312 | +6.3% | 35.8 |
| Sutton town | 2,064 | +4.1% | 42.6 |
| Webster town | 1,972 | +2.9% | 28.2 |
| Bradford town | 1,723 | +3.9% | 35.2 |
| Salisbury town | 1,516 | +6.5% | 39.6 |
| Wilmot town | 1,471 | +4.5% | 29.4 |
| Danbury town | 1,317 | +5.1% | 37.7 |
| Hill town | 1,048 | +3.5% | 26.6 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Merrimack County. Land: 2026 Census Gazetteer. How communities are listed.
Metropolitan area
Merrimack County is a central county of the Concord, NH Micropolitan Statistical Area. Merrimack County is the area’s only county equivalent, so the micro area has the same 932.9 square miles of land. By combined land it ranks #202 of 542 micropolitan areas, and #5 by population. It belongs to the Boston-Worcester-Providence, MA-RI-NH Combined Statistical Area.
ZIP codes
31 ZIP Code Tabulation Areas have land in Merrimack County; 28 of them have most of their land inside the county, and the others mainly cover neighboring areas.
03046031040310603216032200322103224032290323003231032330323403235032420324303255032570325803260032610326303268032730327503276032780328703301033030330403307
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 Merrimack County
Merrimack County shares a land border with 6 county equivalents. It has more land than 5 of them. The largest neighbor is Grafton County (1,708.6 mi²) and the smallest is Strafford County (367.5 mi²). Together with its neighbors, Merrimack County forms a block of 5,520.8 mi² of land, of which it holds 16.9%.
| Bordering county equivalent | Land mi² | Size vs. Merrimack | Compare |
|---|---|---|---|
| Grafton County | 1,708.6 | 1.8× larger | Compare |
| Hillsborough County | 876.5 | 1.1× smaller | Compare |
| Rockingham County | 695.6 | 1.3× smaller | Compare |
| Sullivan County | 537.9 | 1.7× smaller | Compare |
| Belknap County | 401.9 | 2.3× smaller | Compare |
| Strafford County | 367.5 | 2.5× smaller | Compare |
How big is Merrimack County compared with U.S. states?
Merrimack County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.1 times as much. New Hampshire’s county land could hold about 9.6 areas the size of Merrimack County.
Another way to picture it: the same land area would fill a square about 30.5 miles (49.2 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 Merrimack County?
Merrimack County has more land than 2,454 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 Merrimack County at #837 nationally by total area, 69 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 2.3%, compared with a national county-equivalent median of 1.2% — 1.1 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 Merrimack County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #767 | Pacific County, Washington | 933.4 | Compare |
| #768 | Merrimack County, New Hampshire | 932.9 | This county |
| #769 | Grayson County, Texas | 932.8 | 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 43.299579, -71.680041. 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: 2,416,073,588 m²; AWATER: 57,302,049 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 Merrimack County?
Merrimack County, New Hampshire has 932.9 square miles (2,416.1 km²) of land and 22.1 square miles of water, for a total area of 955 square miles. It ranks #768 of 3,222 U.S. county equivalents by land area.
Is Merrimack County the largest county in New Hampshire?
No. Merrimack County ranks #3 of 10 in New Hampshire by land area. The largest is Coos County, with 1,794.6 square miles of land.
What counties border Merrimack County?
Merrimack County shares a land border with Hillsborough County, Belknap County, Sullivan County, Rockingham County, Grafton County, and Strafford County.
What is the population of Merrimack County?
The Census Bureau estimates Merrimack County had 158,078 residents on July 1, 2025, ranking #447 of 3,222 county equivalents. That is 169 people per square mile of land.
What is the county seat of Merrimack County?
The county seat of Merrimack County is Concord.
What cities and towns are in Merrimack County?
Merrimack County has 27 county subdivisions (cities, towns and townships). The most populous five are Concord city, Hooksett town, Franklin city, Bow town, and Pembroke town.
Is Merrimack County part of a metropolitan area?
Yes. It is a central county of the Concord, NH Micropolitan Statistical Area.
How many ZIP codes are in Merrimack County?
31 ZIP Code Tabulation Areas have land in Merrimack County, and 28 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Merrimack County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 1.1 times as much land.
How many acres of land are in Merrimack County?
The land measurement converts to approximately 597,025 acres. Including water, total area is approximately 611,184 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.