County facts · Population growth · October 24, 2026
Fastest Growing Counties in Delaware, 2020 to 2025
Delaware's fastest growing counties by percent and by people added, April 2020 to July 2025 Census estimates, with each official parcel map.
Looking for the fastest growing counties in Delaware? From the Census Bureau's April 1, 2020 estimates base to its July 1, 2025 estimate, Delaware went from about 989,950 to 1,059,952 residents, a change of +70,002 (+7.1%). The fastest growing county by percentage was Sussex County (+16.8%), and it also added the most people (+39,761).
Each table links the county's Platbookmapper page and its official parcel viewer, so you can go from the growth numbers straight to the property lines.
Delaware growth at a glance
- Counties: 3
- Statewide, April 2020 to July 2025: +70,002 residents (+7.1%); July 2024 to July 2025 alone: +9,829 (+0.9%)
- Grew: 3 of 3 · Lost residents: 0
- Fastest growing by percent: Sussex County (+16.8%); most people added: Sussex County (+39,761)
- Counties with more deaths than births over the period: 1 of 3
All 3 Delaware counties ranked by growth
| # | County | Apr 2020 | Jul 2025 | Change | % change | Parcel viewer |
|---|---|---|---|---|---|---|
| 1 | Sussex County | 237,379 | 277,140 | +39,761 | +16.8% | Delaware FirstMap State Parcels |
| 2 | Kent County | 181,849 | 194,786 | +12,937 | +7.1% | Delaware FirstMap State Parcels |
| 3 | New Castle County | 570,722 | 588,026 | +17,304 | +3.0% | Delaware FirstMap State Parcels |
Where the new residents came from
The Census Bureau splits each change into natural change (births minus deaths), net domestic migration (moves from other parts of the US) and net international migration. Totals for April 2020 to July 2025 in all 3 counties:
| County | Births minus deaths | Net domestic moves | Net international moves | Total change |
|---|---|---|---|---|
| Sussex County | −5,529 | +40,989 | +4,325 | +39,761 |
| Kent County | +142 | +10,728 | +2,034 | +12,937 |
| New Castle County | +2,237 | +1,495 | +13,328 | +17,304 |
In 2 of these 3, moves from elsewhere in the US were the biggest source of growth. The three parts do not add up exactly to the total because the Census Bureau also carries a small residual.
The last year alone: July 2024 to July 2025
- Sussex County: +2.2% (+5,907)
- Kent County: +1.0% (+1,910)
- New Castle County: +0.3% (+2,012)
The order for the last year is the same as for the full April 2020 to July 2025 period.
Counties losing residents
Every county in Delaware gained residents between April 2020 and July 2025.
What fast growth means on a parcel map
- New lots show up as plats first. When land is subdivided, the plat is recorded with the county and the parcel layer catches up on its own schedule, so a brand-new lot may not appear on the map for a while. Check the recorder's recent plats if a parcel looks missing.
- Parcel numbers change after splits. A tract that was one parcel last year can be several today. Search by owner name or address as well as by an old parcel number.
- City limits move. Growing cities annex land, which changes who handles zoning and permits even though the county still keeps the deed and the tax map.
- Percent is not the same as people. A small county can post a big percentage on a modest number of new residents, so read the people-added column too.
Related guides
More: All Delaware counties on Platbookmapper
Sources
- U.S. Census Bureau, Population Estimates Program, county totals, Vintage 2025 (April 1, 2020 estimates base and July 1, 2020–2025 estimates, with components of change). Percent change is from the April 1, 2020 estimates base to the July 1, 2025 estimate.
- Platbookmapper county GIS directory (live data file behind our county pages, pulled October 24, 2026) for each official parcel viewer.