Skip to main content
Population Review

Census ACS · 3 counties

Largest Counties in Delaware

Delaware has 3 counties with Census data available. The largest is New Castle County with a population of 573,030. County-level data is important because counties are the primary unit of local government in most states, responsible for courts, elections, public health, and infrastructure. Population distribution across counties reveals where growth is concentrated and where rural decline may be occurring.

Source: Census ACS 5-Year Estimates

#CountyPopulationMedian Income
1Sussex County247,799$78,162
2New Castle County573,030$89,901
3Kent County185,043$72,872

More Rankings for Delaware

Frequently Asked Questions

New Castle County is the #1 ranked county in Delaware by population, with a value of 573,030 according to latest Census ACS data.

Delaware has 3 counties tracked in latest Census ACS data.

All data comes from the American Community Survey (ACS) 5-Year estimates by the US Census Bureau.

Data from the American Community Survey 5-Year estimates. Covers all counties in Delaware.

Source: U.S. Census Bureau ACS, 2026.