| County | Rank | Change (2020) ↓ | 2025 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Sussex County | 1 | 16.61% | 278,293 | 238,654 |
| Kent County | 2 | 7.1% | 195,257 | 182,317 |
| New Castle County | 3 | 4.01% | 593,861 | 570,957 |
Delaware's counties show varied growth patterns from 2020 to 2025. Sussex County leads with 16.61% annualized growth, followed by Kent County (7.1%) and New Castle County (4.01%). The largest counties are New Castle County (593,861), Sussex County (278,293), and Kent County (195,257). All 3 counties in Delaware are growing. Overall, counties averaged 9.24% annualized growth, with total population growing by 7.61% annually.
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