County outline
Where Dukes County is located
Area breakdown
Land accounts for 21% of Dukes County’s measured area and water for 79%. Its combined area converts to 1,271.6 square kilometers or approximately 314,215 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 103.202 | 267.292 | 66,049.3 |
| Water | 387.759 | 1,004.291 | 248,165.8 |
| Total | 490.961 | 1,271.583 | 314,215 |
How Dukes County compares
By original Census land area, Dukes County ranks #12 of 14 in Massachusetts and #3088 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 0.191 times the Massachusetts county-equivalent median of 540.2 square miles. It accounts for 1.3% of the combined county land area in the state.
See the complete Massachusetts ranking · What counts as a county equivalent?
Population and density of Dukes County
The Census Bureau estimates that 21,219 people lived in Dukes County on July 1, 2025. That ranks #1,821 of 3,222 county equivalents nationally and #13 of 14 in Massachusetts. Since the April 1, 2020 estimates base of 20,593, the population has grown by 626 (+3%), compared with +1.7% for Massachusetts as a whole.
With 103.2 square miles of land, that is 206 people per square mile (79 per km²), placing Dukes County #634 nationally for density and #12 in Massachusetts. The median county equivalent has 47 people per square mile; the Massachusetts median is 673. Put another way, there are about 3.1 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 20,580 | 21,110 | 21,081 | 21,063 | 21,354 | 21,219 |
| Change | — | +530 | −29 | −18 | +291 | −135 |
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 Dukes County
Dukes County is divided into 7 cities and towns. In Massachusetts, county subdivisions are local governments, and together they cover all of the county’s land and residents.
The most populous is Edgartown town, with 5,446 residents (25.7% of the county), and it is also the largest by land at 26.8 mi². Among those with at least 1,000 residents in 2020, Edgartown town grew fastest since then (+5.4%).
| County subdivision | Population 2025 | Since 2020 | Land mi² | Share of county land |
|---|---|---|---|---|
| Edgartown townCounty seat | 5,446 | +5.4% | 26.8 | 26% |
| Oak Bluffs town | 5,428 | +1.6% | 7.288 | 7.1% |
| Tisbury town | 4,934 | +2.3% | 6.519 | 6.3% |
| West Tisbury town | 3,645 | +3% | 25 | 24.3% |
| Chilmark town | 1,253 | +3.2% | 19 | 18.4% |
| Aquinnah town | 451 | +1.3% | 5.331 | 5.2% |
| Gosnold town | 62 | −1.6% | 13.2 | 12.8% |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Dukes County. Land: 2026 Census Gazetteer. How communities are listed.
Metropolitan area
Dukes County is a central county of the Vineyard Haven, MA Micropolitan Statistical Area. Dukes County is the area’s only county equivalent, so the micro area has the same 103.2 square miles of land. By combined land it ranks #539 of 542 micropolitan areas, and #505 by population.
ZIP codes
7 ZIP Code Tabulation Areas have land in Dukes County, and each lies mostly inside the county.
02535025390254302557025680257502713
ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Post-office-box and single-address ZIP Codes have no tabulation area.
Counties bordering Dukes County
Dukes County has no land border with another county equivalent in the Census cartographic boundaries: open water separates it from every other county equivalent. Its nearest entries in the national land ranking are listed below, and the Massachusetts directory lists every county equivalent in the state.
How big is Dukes County compared with U.S. states?
Dukes County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 10 times as much. Massachusetts’s county land could hold about 76 areas the size of Dukes County.
Another way to picture it: the same land area would fill a square about 10.2 miles (16.3 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 Dukes County?
Dukes County has more land than 134 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 Dukes County at #2,216 nationally by total area, 872 places closer to the top than its land rank. The water assigned to this geography moves it ahead of some county equivalents with more land.
Its water share is 79%, compared with a national county-equivalent median of 1.2% — 77.8 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 Dukes County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #3087 | York County, Virginia | 104.7 | Compare |
| #3088 | Dukes County, Massachusetts | 103.2 | This county |
| #3089 | Union County, New Jersey | 102.8 | Compare |
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.
Representative coordinates
The Census internal point is 41.380970, -70.701499. It represents a location inside the geography; it is not necessarily the centroid or the address of a courthouse.
Source and precision
U.S. Census Bureau, 2026 Gazetteer Files, Counties. Original ALAND: 267,293,159 m²; AWATER: 1,004,291,291 m². Rankings use ALAND; exact ties use ascending GEOID. Tables preserve Census-published square miles to three decimals, with conversions based on those values.
Common questions
How big is Dukes County?
Dukes County, Massachusetts has 103.2 square miles (267.3 km²) of land and 387.8 square miles of water, for a total area of 491 square miles. It ranks #3088 of 3,222 U.S. county equivalents by land area.
Is Dukes County the largest county in Massachusetts?
No. Dukes County ranks #12 of 14 in Massachusetts by land area. The largest is Worcester County, with 1,510.7 square miles of land.
What counties border Dukes County?
None. Open water separates Dukes County from every other county equivalent in the Census cartographic boundaries.
What is the population of Dukes County?
The Census Bureau estimates Dukes County had 21,219 residents on July 1, 2025, ranking #1,821 of 3,222 county equivalents. That is 206 people per square mile of land.
What is the county seat of Dukes County?
The county seat of Dukes County is Edgartown.
What cities and towns are in Dukes County?
Dukes County has 7 county subdivisions (cities, towns and townships). The most populous five are Edgartown town, Oak Bluffs town, Tisbury town, West Tisbury town, and Chilmark town.
Is Dukes County part of a metropolitan area?
Yes. It is a central county of the Vineyard Haven, MA Micropolitan Statistical Area.
How many ZIP codes are in Dukes County?
7 ZIP Code Tabulation Areas have land in Dukes County, and 7 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Dukes County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 10 times as much land.
How many acres of land are in Dukes County?
The land measurement converts to approximately 66,049 acres. Including water, total area is approximately 314,215 acres. One square mile equals 640 acres.
Why might another source show a different area?
Check whether it reports land or total area, its Census vintage, and its rounding. Our guide explains how to reconcile county area figures.
Can this establish a property boundary?
No. Statistical measurements and generalized maps do not establish property lines. Consult the relevant local surveying or land-records authority.