Montgomery County, Maryland

The most populous of Maryland's 24 counties.

CountyFIPS 24031

Within Maryland

Montgomery County, highlighted, with the areas around it. Boundaries generalised from the 2025 Census cartographic boundary file; neighbour fills carry no data. The dot marks Rockville, the county seat, located via the 2025 Census Gazetteer.

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Population: 1,074,582; +13,656 (+1.3%) since 2020
Land area: 493.1; square miles. A further 2.7% of the total area is water
Population density: 2,179; people per square mile, computed rather than published
County seat: Rockville; Seat of county government.
Established: 1776; 249 years ago
Largest city: Gaithersburg city; Population 71,113.

Satellite view

Aerial imagery of Montgomery County with its boundary drawn on top. A map shows you the shape; this shows you what is inside it, and which side of the line a place falls on.

Aerial view of Montgomery County, Maryland from the USGS National Map, with its boundary outlined — Imagery: USGS National Map, USGS Imagery Only, public domain, requested from USGS by your browser when you reach this point on the page, at 800 by 690 pixels. The boundary is the 2025 Census cartographic boundary file, reprojected to Web Mercator to match the imagery. You can also open the USGS National Map viewer.

Where Montgomery County ranks

Position among the 24 counties of Maryland, and among all 3,144 US counties and county-equivalents. Computed from the figures on this page.

Measure	Value	In Maryland	Nationally
Population	1,074,582	1st of 24	45th of 3,144
Land area	493.1 sq mi	5th of 24	2,108th of 3,144
Population density	2,179 per sq mi	2nd of 24	65th of 3,144
Median household income	$132,450	3rd of 24	25th of 3,143

Full data for Montgomery County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
Measure	Value	Source and vintage
Population	1,074,582	Vintage 2025 Population Estimates
Population in 2020	1,060,926	Vintage 2025 Population Estimates
2020 estimates base?	1,062,079	Vintage 2025 Population Estimates
Land area	493.1 sq mi	2025 Gazetteer Files
Water area	13.8 sq mi	2025 Gazetteer Files
Total area	506.9 sq mi	2025 Gazetteer Files
Population density?	2,179 per sq mi	Computed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income	$132,450	American Community Survey 2020-2024 5-Year Estimates
Median home value	$640,300	American Community Survey 2020-2024 5-Year Estimates
Median age	40.2	American Community Survey 2020-2024 5-Year Estimates
Households	389,210	American Community Survey 2020-2024 5-Year Estimates
Housing units	406,531	American Community Survey 2020-2024 5-Year Estimates

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026. Population density is computed here, not published: it divides the Vintage 2025 population estimate by the 2025 Gazetteer land area, which are two different Census products. Retrieved 30 August 2026.

How the population changed

The Census Bureau publishes the components behind an estimate, not just the total. For the year to July 2025:

Births minus deaths: +4,327; 11,074 births, 6,747 deaths
Net migration: -2,776; More people moved out than moved in.

Source: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026. Retrieved 30 August 2026.

The 7 areas bordering Montgomery County

Ordered by the length of the border actually shared, which the Census Bureau publishes in its county adjacency file and which no other county reference presents.

Bordering area	State	Shared border	Population
Howard County	Maryland	31 mi	339,183
Loudoun County	Virginia	21 mi	449,749
Frederick County	Maryland	18 mi	302,883
Fairfax County	Virginia	18 mi	1,167,873
Prince George's County	Maryland	14 mi	970,374
District of Columbia	District of Columbia	8.9 mi	693,645
Arlington County	Virginia	13 ft	243,931

Source: US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. Retrieved 30 August 2026.

Side by side

All 24 counties of Maryland

Open the interactive Maryland county map, or jump straight to any of them.

Data on this page last rebuilt 30 August 2026. How these figures are produced.