What are the fastest-growing counties in Delaware?
Sussex County is the fastest-growing county in Delaware: its population grew 3.04% a year from 2020 to 2025, to 277,140 residents (Census PEP Vintage 2025). Kent County (1.33%) and New Castle County (0.59%) follow. Delaware as a whole grew 1.34% a year to 1,059,952 residents.
Data as of 2026-09-23. Population, growth and migration: PEP Vintage 2025 · 2020–2025. Income migration: IRS SOI 2022–2023 (2-yr lag).
Top 3 counties in Delaware by population growth, 2020 to 2025
| Rank | County | Population | Growth (% per year) | Net domestic migration | Net international migration | IRS net AGI migration |
|---|---|---|---|---|---|---|
| 1 | Sussex County | 277,140 | 3.04% | +39,199 | +4,319 | +$517.2M |
| 2 | Kent County | 194,786 | 1.33% | +10,286 | +2,023 | +$47.7M |
| 3 | New Castle County | 588,026 | 0.59% | +1,492 | +13,281 | -$0.9M |
Where are people moving in Delaware?
Sussex County gained the most people from elsewhere in the United States: net domestic migration of +39,199 from 2020 to 2025 (Census PEP Vintage 2025). The table ranks every Delaware place with 10,000 or more residents by that figure; the IRS column shows net adjusted gross income migration for 2022 to 2023.
| Rank | County | Population | Growth (% per year) | Net domestic migration | Net international migration | IRS net AGI migration |
|---|---|---|---|---|---|---|
| 1 | Sussex County | 277,140 | 3.04% | +39,199 | +4,319 | +$517.2M |
| 2 | Kent County | 194,786 | 1.33% | +10,286 | +2,023 | +$47.7M |
| 3 | New Castle County | 588,026 | 0.59% | +1,492 | +13,281 | -$0.9M |
Go past the headline numbers
The interactive Demographics map layer and the full report for a single place are part of paid plans.
Get the Demographics Report for Sussex CountyFrequently asked questions
- What are the fastest-growing counties in Delaware?
- By population growth from 2020 to 2025, the fastest are Sussex County (3.04% a year), Kent County (1.33% a year) and New Castle County (0.59% a year) (Census PEP Vintage 2025). Only places with 10,000 or more residents are ranked.
- Where are people moving in Delaware?
- By net domestic migration from 2020 to 2025, the largest gains are Sussex County (+39,199), Kent County (+10,286) and New Castle County (+1,492) (Census PEP Vintage 2025).
- How fast is Delaware growing overall?
- Delaware grew 1.34% a year from 2020 to 2025, to 1,059,952 residents, with net migration of +70,600 people (Census PEP Vintage 2025).
- Where does this Delaware data come from, and how current is it?
- Population, growth and migration come from the U.S. Census Bureau Population Estimates Program (PEP Vintage 2025 · 2020–2025). Income migration comes from IRS Statistics of Income (IRS SOI 2022–2023 (2-yr lag)). Counties with fewer than 10,000 residents are not ranked. Data last loaded 2026-09-23.
Data as of 2026-09-23: sources and periods
- Population, growth and migration
- U.S. Census Bureau, Population Estimates Program: PEP Vintage 2025 · 2020–2025. census.gov/programs-surveys/popest
- Income migration (net AGI)
- Internal Revenue Service, Statistics of Income migration data: IRS SOI 2022–2023 (2-yr lag). irs.gov/statistics/soi-tax-stats-migration-data
How to read the table
- Population is the Census July 1 estimate of the latest vintage.
- Growth is the compound annual rate over 2020 to 2025.
- Net domestic and international migration are cumulative people over 2020 to 2025.
- IRS net AGI migration is adjusted gross income that moved in, less what moved out, for 2022 to 2023. A plus sign means a net inflow.
- Places with fewer than 10,000 residents are left out of the rankings.