Delaware Counties by Population (2026)
2026 Pop.
200K
250K
300K
350K
400K
450K
500K
550K
Top 5 Most Populous Counties
| County | 2026 Pop. ↓ | Area (mi²) | Density (/mi²) | Change (2020) |
|---|---|---|---|---|
| New Castle County | 599,629 | 426 | 1,408 | 5.02% |
| Sussex County | 285,452 | 936 | 305 | 19.61% |
| Kent County | 197,824 | 586 | 338 | 8.51% |
Sources
- US Census State Population Estimates - Most recent state estimates from the Census Bureau's Population Estimates Program
- US Census County Population Estimates - Most recent county estimates from the Census Bureau's Population Estimates Program
- American Community Survey (2009 - 2013)
- Census QuickFacts
- Historical Populations of States and Counties (1790 - 1990)