Montgomery County, Maryland

Montgomery County is a county in Maryland, United States, directly north of Washington, D.C.
It had a population of 1,062,061 at the 2020 census, up 9.3 percent from 971,777 in 2010, and an
estimated 1,074,582 by 2024. The county covers 493.11 square miles (1,277 km2) of land, centred
near 39°08′N 77°12′W.

Rockville is the county seat; its postal code is 20850. Gaithersburg, its neighbor along
Interstate 270, is technically the county’s largest incorporated city by a slim margin, and
Germantown, an unincorporated community, outsizes them both. The county holds 3 incorporated
cities, 15 incorporated towns and dozens of unincorporated communities, and it runs on Eastern
Time. Its FIPS code is 24031.

Towns & Villages in Montgomery County

Montgomery County has 18 incorporated municipalities and dozens more unincorporated communities
recognized as census-designated places (CDPs). Maryland does not use civil townships, so every
place here answers to the county government directly unless it has its own charter. The table
below lists all 18 incorporated places, then the county’s 25 largest CDPs by population.

Six of the incorporated towns above cluster around one name. The Town of Chevy Chase, Chevy
Chase Village, Chevy Chase View, Martin’s Additions and Chevy Chase Sections Three and Five are
five separate incorporated municipalities, each with its own mayor and council, all carved out of
the historic Chevy Chase streetcar suburb and all sharing the 20815 ZIP. A sixth area, simply
called Chevy Chase, is unincorporated and appears in the CDP table below. Takoma Park’s population
figure is citywide; part of the city’s built-up east side actually sits across the line in Prince
George’s County.

Beyond these 25, another dozen or so smaller CDPs are on record, among them Ashton-Sandy Spring,
Darnestown, Forest Glen, Layhill, Leisure World, South Kensington, Spencerville and Ten Mile
Creek. None of Montgomery’s CDPs has its own government; each is governed directly by the county
and, for the parts inside the Washington Beltway, often also by a citizens’ advisory board.

ZIP Codes

Montgomery County uses roughly sixty ZIP codes in the 20812–20918 range, too many to list
individually. Rockville’s core ZIP is 20850, with 20851 through 20855 covering the rest of the
city; Gaithersburg runs 20877 through 20879 plus 20882 and 20886; Bethesda centers on 20814, with
20810, 20811, 20816 and 20817 nearby; Silver Spring spans 20901 through 20906 and 20910;
Germantown uses 20874 and 20876. Takoma Park is 20912, Potomac is 20854, Olney is 20832, Damascus
is 20872 and Poolesville is 20837. Smaller places without a dedicated ZIP, including several of
the unincorporated CDPs east of Route 29, share their mailing code with the nearest post office
town rather than carrying one of their own.

Geography

Montgomery County sits in Maryland’s Piedmont region, sloping from rolling hills in the north
down to the fall line near the Potomac River in the south. Of its total area, 493.11 square miles
are land and 13.80 square miles are water — the Potomac forms the county’s entire
southwestern border, and the Chesapeake and Ohio Canal National Historical Park runs along that
riverbank for the county’s full length. Great Falls, where the Potomac drops through a narrow
gorge, is the county’s best-known natural landmark. The northern half of the county, around
Damascus and Poolesville, stays largely agricultural and is protected under Maryland’s
Agricultural Reserve, a zoning district that has kept roughly a third of the county’s land
undeveloped since 1980.

Frederick County lies to the north and northwest, and Prince George’s County lies to the east
and southeast; neither currently has a live profile on this site. The county touches Carroll
County at a single point to the northeast — Carroll County
— and shares a longer line with Howard County
to the east. Washington, D.C. borders the county directly to the south. Across the Potomac to the
west and southwest lie Virginia’s Loudoun County
and Fairfax County.

Demographics

Montgomery County had a population of 1,062,061 at the 2020 census, the largest of any county
in Maryland, and the latest estimate puts it near 1,074,582. Germantown and Silver Spring, both
unincorporated, are the two largest communities in the county, each outsizing every incorporated
city. Median household income runs about $132,450, well above Maryland’s statewide figure of
$98,678 (2023 ACS). Population density works out to roughly 2,154 people per square mile of land,
among the densest counties in the state outside Baltimore City.

Economy & Local Life

Professional, scientific and technical services is the county’s largest employment sector,
followed by health care and social assistance and then public administration. The federal
government anchors much of that: the National Institutes of Health’s main campus sits in
Bethesda, the Food and Drug Administration’s White Oak campus is one of the region’s largest
federal worksites, and the National Institute of Standards and Technology is headquartered in
Gaithersburg. Around that federal core, the county has built one of the country’s larger
biotechnology clusters, with the Interstate 270 corridor through Rockville and Gaithersburg often
called Maryland’s biotech corridor. Private employers based in the county include Marriott
International, Lockheed Martin, Adventist HealthCare and GEICO. Montgomery County Public Schools,
the largest school system in Maryland, is the county’s single biggest employer. The county’s
biggest annual event is the Montgomery County Agricultural Fair each August at the fairgrounds in
Gaithersburg, one of the longest continuously running county fairs in the state.

History

The Maryland General Assembly created Montgomery County on 6 September 1776, carving it out of
Frederick County in the same act that created Washington County — the first two Maryland
counties named for Revolutionary War figures rather than English places. The county was named for
Major General Richard Montgomery, killed leading the American assault on Quebec in December 1775.
Rockville became the county seat in the early 19th century.

The Chesapeake and Ohio Canal, built along the county’s Potomac River border between 1828 and
1850 to move coal and farm goods to Georgetown, operated until a 1924 flood ended commercial
traffic; the towpath is now a National Historical Park. In the decades before the Civil War, the
Sandy Spring area in the county’s east was a center of Quaker abolitionist activity and Underground
Railroad activity, documented today at the Woodlawn Manor Cultural Park.

Getting There

Interstate 270 runs northwest from the Capital Beltway through Rockville, Gaithersburg and
Germantown toward Frederick; Interstate 495, the Capital Beltway, crosses the county’s southern
end. US 29 and Maryland Route 355 (Rockville Pike/Wisconsin Avenue) are the county’s other main
north-south routes.

• Washington, D.C. — about 12 miles south of Rockville
• Frederick — about 20 miles northwest
• Baltimore — about 45 miles northeast
• Annapolis — about 40 miles southeast

Ronald Reagan Washington National Airport, about 20 miles south of Rockville, is the nearest
major commercial airport; Washington Dulles International, in Virginia, is a comparable distance
southwest. Washington Union Station, roughly 15 miles south, is the nearest Amtrak stop. MARC’s
Brunswick Line runs commuter trains from Union Station through the county, stopping at Silver
Spring, Kensington, Garrett Park, Rockville and Germantown. Metro’s Red Line also crosses the
county, serving Bethesda, Rockville, Silver Spring, Wheaton and Glenmont among other stations.

Frequently Asked Questions

Where is Montgomery County located?
It sits in central Maryland, directly north of Washington, D.C., bordered by Frederick, Carroll,
Howard and Prince George’s counties and, across the Potomac River, by Virginia’s Loudoun and
Fairfax counties.

What is the population of Montgomery County?
1,062,061 at the 2020 census, with an estimate near 1,074,582 by 2024 — the most populous
county in Maryland.

How big is Montgomery County?
493.11 square miles (1,277 km2) of land, plus 13.80 square miles of water along the Potomac
River.

What is the county seat of Montgomery County?
Rockville, postal code 20850. Neighboring Gaithersburg is slightly larger by population.

How many towns and cities are in Montgomery County?
18 incorporated municipalities — 3 cities and 15 towns — plus dozens of unincorporated
communities recognized as census-designated places, the largest being Germantown and Silver
Spring.

What ZIP codes does Montgomery County use?
Around 60 codes in the 20812–20918 range, including 20850 for Rockville, 20877–20879
for Gaithersburg, 20814 for Bethesda and 20910 for Silver Spring.

What is Montgomery County known for?
Its federal biotech and research campuses — the NIH in Bethesda, FDA in White Oak and NIST
in Gaithersburg — and the Agricultural Reserve, a protected farmland zone covering roughly a
third of the county.

More counties in this state: Towns and villages in Maryland.