Plymouth County area

Population and density of Plymouth County

The Census Bureau estimates that 546,829 people lived in Plymouth County on July 1, 2025. That ranks #133 of 3,222 county equivalents nationally and #7 of 14 in Massachusetts. Since the April 1, 2020 estimates base of 530,818, the population has grown by 16,011 (+3%), compared with +1.7% for Massachusetts as a whole.

With 658.5 square miles of land, that is 830 people per square mile (321 per km²), placing Plymouth County #222 nationally for density and #6 in Massachusetts. The median county equivalent has 47 people per square mile; the Massachusetts median is 673. Put another way, there are about 0.771 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 Plymouth County

Plymouth County is divided into 27 cities and towns. In Massachusetts, county subdivisions are local governments, and together they cover all of the county’s land and residents.

The most populous is Brockton city, with 106,134 residents (19.4% of the county). The largest by land is Plymouth town, at 96.4 mi², or 14.6% of the county’s land. The county seat, Plymouth town, has 67,846 residents. Among those with at least 1,000 residents in 2020, Plymouth town grew fastest since then (+10.8%).

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

Metropolitan area

Plymouth County is a central county of the Boston-Cambridge-Newton, MA-NH Metropolitan Statistical Area, in the Boston, MA metropolitan division. Its 7 county equivalents have 5,034,221 residents on 3,486.3 square miles of land; Plymouth County accounts for 18.9% of the land and 10.9% of the residents. By combined land it ranks #84 of 393 metropolitan areas, and #11 by population. It belongs to the Boston-Worcester-Providence, MA-RI-NH Combined Statistical Area.

ZIP codes

36 ZIP Code Tabulation Areas have land in Plymouth County; 35 of them have most of their land inside the county, and the others mainly cover neighboring areas.

020430204502047020500206102066023010230202324023250233002332023330233802339023410234602347023500235102359023600236402366023670237002379023820253202538025580257102576027380273902770

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 Plymouth County

Plymouth County shares a land border with 3 county equivalents. It has more land than every one of them. The largest neighbor is Bristol County (553.1 mi²) and the smallest is Barnstable County (394.2 mi²). Together with its neighbors, Plymouth County forms a block of 2,001.9 mi² of land, of which it holds 32.9%.

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

Plymouth County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.6 times as much. Massachusetts’s county land could hold about 12 areas the size of Plymouth County.

Another way to picture it: the same land area would fill a square about 25.7 miles (41.3 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 Plymouth County?

Plymouth County has more land than 1,796 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 Plymouth County at #672 nationally by total area, 754 places closer to the top than its land rank. The water assigned to this geography moves it ahead of some county equivalents with more land.

Its water share is 39.8%, compared with a national county-equivalent median of 1.2% — 38.6 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 Plymouth 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.