Montgomery County area

Population and density of Montgomery County

The Census Bureau estimates that 1,074,582 people lived in Montgomery County on July 1, 2025. That ranks #45 of 3,222 county equivalents nationally and #1 of 24 in Maryland. Since the April 1, 2020 estimates base of 1,062,079, the population has grown by 12,503 (+1.2%), compared with +1.4% for Maryland as a whole.

With 493.1 square miles of land, that is 2,179 people per square mile (841 per km²), placing Montgomery County #73 nationally for density and #2 in Maryland. The median county equivalent has 47 people per square mile; the Maryland median is 335. Put another way, there are about 0.294 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 Montgomery County

19 incorporated places lie at least partly in Montgomery County. Together they are home to 177,030 people (16.5%); the other 897,552 (83.5%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Gaithersburg city, with 71,113 residents in the county. The county seat, Rockville city, has 67,563 residents. By land, Rockville city is the largest at 13.6 mi². Among places with at least 1,000 residents in 2020, Kensington town grew fastest since then (+25.3%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Montgomery County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.

Metropolitan area

Montgomery County is a central county of the Washington-Arlington-Alexandria, DC-VA-MD-WV Metropolitan Statistical Area, in the Frederick-Gaithersburg-Bethesda, MD metropolitan division. Its 23 county equivalents have 6,465,724 residents on 6,033.7 square miles of land; Montgomery County accounts for 8.2% of the land and 16.6% of the residents. By combined land it ranks #35 of 393 metropolitan areas, and #7 by population. It belongs to the Washington-Baltimore-Arlington, DC-MD-VA-WV-PA Combined Statistical Area.

ZIP codes

53 ZIP Code Tabulation Areas have land in Montgomery County; 48 of them have most of their land inside the county, and the others mainly cover neighboring areas.

2070520707207772081220814208152081620817208182083220833208372083820839208412084220850208512085220853208542085520860208612086220866208682087120872208742087620877208782087920880208822088620889208922089420895208962089920901209022090320904209052090620910209122177121797

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 Montgomery County

Montgomery County shares a land border with 6 county equivalents, including 3 in Virginia and District of Columbia. It has more land than 4 of them. The largest neighbor is Frederick County (660.7 mi²) and the smallest is District of Columbia (61.1 mi²). Together with its neighbors, Montgomery County forms a block of 2,855.2 mi² of land, of which it holds 17.3%.

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

Montgomery County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 2.1 times as much. Maryland’s county land could hold about 20 areas the size of Montgomery County.

Another way to picture it: the same land area would fill a square about 22.2 miles (35.7 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 Montgomery County?

Montgomery County has more land than 1,114 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 Montgomery County at #2,148 nationally by total area, 40 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 2.7%, compared with a national county-equivalent median of 1.2% — 1.5 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 Montgomery 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.