Middlesex County, Massachusetts

County seats: Cambridge and Lowell · Population 1.7 million (2025) · 818 sq mi

Middlesex County is the most populous of Massachusetts's 14 counties, with 1,669,979 people (2025 estimate). It has 2 county seats: Cambridge and Lowell. The map shows its 13 cities and towns and the 5 neighboring counties.

Map of Middlesex County, Massachusetts with cities, towns and the county boundary
Middlesex County, Massachusetts with its cities and towns, unincorporated communities (CDPs) and neighboring counties. Boundaries: U.S. Census Bureau, 2025. Free to use with attribution (CC BY 4.0).
Download PDF (Letter) 183 KBPNG image 145 KBMassachusetts county map

Middlesex County facts

County seats
Cambridge, Lowell
Population (2025 estimate)
1,669,979 +2.3% since 2020
Land area
818 sq mi 3rd largest of 14
Water area
29 sq mi
Population density
2,042 per sq mi
Established
1643
Same name
One of 3 Middlesex Counties in the US
Named after
Middlesex historic county of England
Largest city
Cambridge 122,588
Median household income
$130,847
Cities and towns
13 plus 24 CDPs
ZIP codes
83
Time zone
Eastern
FIPS code
25017

Cities and towns in Middlesex County

Middlesex County has 13 incorporated cities, towns and villages. Populations count the people living inside Middlesex County; cities that cross a county line also list the other counties.

NameTypePopulation 2025Also in
Cambridge (county seat)City122,588
Lowell (county seat)City119,971
NewtonCity90,741
SomervilleCity84,211
FraminghamCity73,021
MaldenCity66,370
WalthamCity65,037
MedfordCity59,834
EverettCity53,572
WoburnCity43,962
MarlboroughCity42,772
WatertownCity35,710
MelroseCity29,597

Unincorporated communities (CDPs)

Census-designated places are communities without their own city government; the county provides their services.

CommunityPopulationAlso in
Arlington46,350
Lexington34,295
Wakefield27,793
Belmont27,175
Burlington26,274
Reading25,612
Winchester23,406
Stoneham23,355
Wilmington23,336
Hudson15,719
Maynard10,712
Pinehurst6,845
Cochituate6,471
West Concord5,876
Hopkinton3,426
Littleton Common3,289
Ayer3,098
Hanscom AFB2,110
Pepperell1,971
East Pepperell1,949
Groton1,232
Shirley1,146
Townsend987
Devens283Worcester County

ZIP codes in Middlesex County

83 ZIP codes reach into Middlesex County. ZIP codes ignore county lines, so some also cover a neighboring county.

Population of Middlesex County, 2020–2025

Middlesex County grew by 38,067 people (+2.3%) between April 2020 and July 2025: 18,568 more births than deaths and a net gain of 21,032 people from migration.

Year (July 1)Population
20201,624,461
20211,614,929
20221,630,890
20231,644,193
20241,663,929
20251,669,979

Neighboring counties

Printable Middlesex County map

The PDF is a vector file with real text: it prints sharp on Letter paper and you can search it for a town. The PNG is 2400 pixels wide for slides and documents. Both are free to use with a credit to WhichCounty.

Paste this code to embed the map on your site:

Sources

Back to the Massachusetts county map with all 14 counties. Found an error? Tell us.