| County | Rank | Change (2020) ↓ | 2025 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Sussex County | 1 | 16.35% | 277,633 | 238,629 |
| Kent County | 2 | 6.33% | 193,851 | 182,315 |
| New Castle County | 3 | 2.51% | 585,268 | 570,918 |
Delaware's counties show varied growth patterns from 2020 to 2025. Sussex County leads with 16.35% annualized growth, followed by Kent County (6.33%) and New Castle County (2.51%). The largest counties are New Castle County (585,268), Sussex County (277,633), and Kent County (193,851). All 3 counties in Delaware are growing. Overall, counties averaged 8.4% annualized growth, with total population growing by 6.54% annually.