Hillsborough County area

Population and density of Hillsborough County

The Census Bureau estimates that 433,415 people lived in Hillsborough County on July 1, 2025. That ranks #177 of 3,222 county equivalents nationally and #1 of 10 in New Hampshire. Since the April 1, 2020 estimates base of 422,944, the population has grown by 10,471 (+2.5%), compared with +2.7% for New Hampshire as a whole.

With 876.5 square miles of land, that is 494 people per square mile (191 per km²), placing Hillsborough County #340 nationally for density and #1 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 1.3 acres of land per resident.

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 Hillsborough County

Hillsborough County is divided into 31 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 Manchester city, with 116,818 residents (27% of the county). The largest by land is Weare town, at 59.1 mi², or 6.7% of the county’s land. Among those with at least 1,000 residents in 2020, Merrimack town grew fastest since then (+11.5%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Hillsborough County. Land: 2026 Census Gazetteer. How communities are listed.

Metropolitan area

Hillsborough County is a central county of the Manchester-Nashua, NH Metropolitan Statistical Area. Hillsborough County is the area’s only county equivalent, so the metro area has the same 876.5 square miles of land. By combined land it ranks #297 of 393 metropolitan areas, and #130 by population. It belongs to the Boston-Worcester-Providence, MA-RI-NH Combined Statistical Area.

ZIP codes

34 ZIP Code Tabulation Areas have land in Hillsborough County, and each lies mostly inside the county.

03031030330304303045030470304803049030510305203054030550305703060030620306303064030700307103076030820308403086031010310203103031040310903110032440328103440034420344903458

ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Post-office-box and single-address ZIP Codes have no tabulation area.

Counties bordering Hillsborough County

Hillsborough County shares a land border with 7 county equivalents, including 3 in Massachusetts. It has more land than 5 of them. The largest neighbor is Worcester County (1,510.7 mi²) and the smallest is Essex County (492.5 mi²). Together with its neighbors, Hillsborough County forms a block of 6,570.6 mi² of land, of which it holds 13.3%.

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

Hillsborough County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.2 times as much. New Hampshire’s county land could hold about 10 areas the size of Hillsborough County.

Another way to picture it: the same land area would fill a square about 29.6 miles (47.6 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 Hillsborough County?

Hillsborough County has more land than 2,301 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 Hillsborough County at #1,002 nationally by total area, 81 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% — 0.6 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 Hillsborough County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

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.