Frederick County area

Population and density of Frederick County

The Census Bureau estimates that 302,883 people lived in Frederick County on July 1, 2025. That ranks #246 of 3,222 county equivalents nationally and #7 of 24 in Maryland. Since the April 1, 2020 estimates base of 271,710, the population has grown by 31,173 (+11.5%), compared with +1.4% for Maryland as a whole.

With 660.7 square miles of land, that is 458 people per square mile (177 per km²), placing Frederick County #367 nationally for density and #8 in Maryland. The median county equivalent has 47 people per square mile; the Maryland median is 335. Put another way, there are about 1.4 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 Frederick County

12 incorporated places lie at least partly in Frederick County. Together they are home to 130,834 people (43.2%); the other 172,049 (56.8%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Frederick city, with 92,059 residents in the county. Among places with at least 1,000 residents in 2020, Brunswick city grew fastest since then (+20.6%).

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

Metropolitan area

Frederick County is an outlying 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; Frederick County accounts for 10.9% of the land and 4.7% 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

35 ZIP Code Tabulation Areas have land in Frederick County; 28 of them have most of their land inside the county, and the others mainly cover neighboring areas.

2084220871217012170221703217042170521710217142171621717217182171921727217542175521757217582176221769217702177121773217742177621777217782178021783217872178821790217912179321798

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 Frederick County

Frederick County shares a land border with 6 county equivalents, including 3 in Virginia and Pennsylvania. It has more land than 5 of them. The largest neighbor is Franklin County (772.3 mi²) and the smallest is Carroll County (447.6 mi²). Together with its neighbors, Frederick County forms a block of 3,865.8 mi² of land, of which it holds 17.1%.

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

Frederick 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. Maryland’s county land could hold about 15 areas the size of Frederick County.

Another way to picture it: the same land area would fill a square about 25.7 miles (41.4 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 Frederick County?

Frederick County has more land than 1,800 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 Frederick County at #1,524 nationally by total area, 102 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 1%, compared with a national county-equivalent median of 1.2% — 0.2 percentage points lower. 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 Frederick 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.