New Castle County Flag

New Castle County

State:
Delaware
County Seat:
Wilmington

New Castle County's estimated 2026 population is 599,629 with a growth rate of 0.97% in the past year according to the most recent United States census data. New Castle County is the largest county in Delaware. The 2010 population was 538,792 and has seen a growth of 11.29% since that time.

599,629
Total Population
1,408
Population Density (mi²)
1
Population Rank (State)
5.8K 0.97%
Annual Population Growth

New Castle County Population

Demographics

Economics and Income Statistics