Sussex County area

Population and density of Sussex County

The Census Bureau estimates that 277,140 people lived in Sussex County on July 1, 2025. That ranks #269 of 3,222 county equivalents nationally and #2 of 3 in Delaware. Since the April 1, 2020 estimates base of 237,379, the population has grown by 39,761 (+16.8%), compared with +7.1% for Delaware as a whole.

With 936.2 square miles of land, that is 296 people per square mile (114 per km²), placing Sussex County #515 nationally for density and #3 in Delaware. The median county equivalent has 47 people per square mile; the Delaware median is 332. Put another way, there are about 2.2 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 Sussex County

25 incorporated places lie at least partly in Sussex County. Together they are home to 69,288 people (25%); the other 207,852 (75%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Seaford city, with 9,165 residents in the county. The county seat, Georgetown town, has 8,291 residents. By land, Milford city is the largest at 9.862 mi² across all its counties. Among places with at least 1,000 residents in 2020, Millville town grew fastest since then (+16.9%).

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

Metropolitan area

Sussex County is a central county of the Seaford, DE Micropolitan Statistical Area. Sussex County is the area’s only county equivalent, so the micro area has the same 936.2 square miles of land. By combined land it ranks #200 of 542 micropolitan areas, and #1 by population.

ZIP codes

24 ZIP Code Tabulation Areas have land in Sussex County; 22 of them have most of their land inside the county, and the others mainly cover neighboring areas.

199301993119933199391994019941199441994519947199501995119952199561995819960199631996619967199681997019971199731997521874

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 Sussex County

Sussex County shares a land border with 5 county equivalents, including 4 in Maryland. It has more land than every one of them. The largest neighbor is Kent County (586.1 mi²) and the smallest is Caroline County (319.4 mi²). Together with its neighbors, Sussex County forms a block of 3,225.2 mi² of land, of which it holds 29%.

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

Sussex County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.1 times as much. Delaware’s county land could hold about 2.1 areas the size of Sussex County.

Another way to picture it: the same land area would fill a square about 30.6 miles (49.2 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 Sussex County?

Sussex County has more land than 2,460 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 Sussex County at #591 nationally by total area, 171 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 21.8%, compared with a national county-equivalent median of 1.2% — 20.6 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 Sussex 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.