New Castle County, Delaware Population 2026
Updated April 2026 · US Census ACS 2023 5-Year Estimates · 1st-largest in Delaware
The population of New Castle County, Delaware is 573,030 as of the 2023 American Community Survey, making it the 1st-largest county in Delaware. The median household income is $89,901, the median home value is $329,800, and the median age is 39.2.
The population of New Castle County has grown 9.2% since 2010 (538,792 → 588,093), a +0.63% annualized rate.
573,030
Population
+0.63%
Annual growth
1344
People / sq mi
$89,901
Median Income
$329,800
Median Home Value
New Castle County covers 426 sq mi of land at 1344.1 people per square mile.
About New Castle County, DE
New Castle County stands apart on settlement density — it is among the most densely settled of US counties, at roughly 1,344 people per square mile. With 573,030 residents, New Castle County is a county in Delaware. It is the #1-largest of all counties in Delaware nationally.
Households here are among the highest-earning of all US counties: median income is $89,901, above the US median of $78,538. The poverty rate, 6.7%, is on the lower side for US counties and below the national 12.4%. The median home value is $329,800, with typical rent around $1,379.
New Castle County is among the best-educated US counties: 39.2% of adults 25 and older hold a bachelor’s degree, above the national 35.0%. Remote work is widespread — 15.5% of workers stay home, above the national 14.0%, and the average commute runs about 25 minutes each way.
That density explains much of the rest of the profile in New Castle County: denser places lean toward renting, shorter commutes by transit, and a younger working-age mix.
New Castle County Population History (2010-2024)
The county of New Castle County had a population of 538,792 in 2010 and 588,093 in 2024, a 9.2% growth over 14 years. The peak was 588,093 in 2024. Average annual growth rate: 0.63%.
588,093
Population (2024)
538,792
Population (2010)
588,093
Peak (2024)
0.63%
Avg Annual Growth
| Year | Population |
|---|---|
| 2010 | 538,792 |
| 2011 | 542,031 |
| 2012 | 545,053 |
| 2013 | 548,614 |
| 2014 | 551,124 |
| 2015 | 553,929 |
| 2016 | 555,582 |
| 2017 | 556,491 |
| 2018 | 557,983 |
| 2019 | 559,941 |
| 2020 | 570,957 |
| 2021 | 572,116 |
| 2022 | 576,316 |
| 2023 | 582,325 |
| 2024 | 588,093 |
Race & Ethnicity
| White | 56.5% |
| Black or African American | 25.3% |
| Asian | 0.0% |
| Hispanic or Latino (any race) | 1.1% |
| Two or More Races | 0.0% |
Age & Sex
39.2
Median Age
51.5%
Female
48.5%
Male
16.5%
Age 65+
Age Distribution
Children (under 15): 17.5% · Seniors (65+): 16.5%
Income & Poverty
| Median household income | $89,901+$7,046 vs state |
| Mean household income | $118,003 |
| Per-capita income | $46,990 |
| Poverty rate | 6.7%-0.6% vs state |
| Unemployment rate | 3.2% |
| Employment-to-population | 62.6% |
Top Industries by Employment
The largest employment sector in New Castle County is professional & business services, accounting for 25.2% of workers.
How residents commute
2.6%
Drive alone
2.2%
Carpool
70.7%
Public transit
15.5%
Work from home
25.4 min
Avg commute
Housing
$329,800+$3,000 vs state
Median home value
$1,379
Median rent
68.5%
Homeownership rate
235,057
Total housing units
94.8%
Occupied
5.2%
Vacant
31.5%
Renter-occupied
Social & access
94.3%
With health insurance
96.3%
With broadband internet
40.9%
Foreign-born
6.1%
Veterans (18+)
12.8%
With a disability
83.4%
Speak language other than English at home
Education
92.6%
High School+
39.2%
Bachelor's+
Largest cities in Delaware
Other counties in Delaware
Part of Delaware
Metro areas in Delaware
County rankings
Common questions about New Castle County, DE
Frequently Asked Questions
New Castle County, Delaware has a population of 573,030 according to the US Census Bureau's 2023 American Community Survey 5-year estimates, making it the 1st-largest county in Delaware. Population density is 1344 people per square mile.
The population of New Castle County has grown 9.2% since 2010 (538,792 → 588,093), a +0.63% annualized rate.
The median household income in New Castle County, Delaware is $89,901, with mean (average) household income of $118,003 and per-capita income of $46,990. 6.7% of residents live below the federal poverty level.
In New Castle County, the largest racial and ethnic groups are White (56.5%), Black or African American (25.3%), Hispanic or Latino (1.1%). Figures are from the US Census Bureau's 2023 ACS 5-year estimates and reflect self-reported responses.
The median age in New Castle County, Delaware is 39.2 years. Residents are 51.5% female and 48.5% male.
The median home value in New Castle County is $329,800 and median monthly rent is $1,379. 68.5% of occupied housing units are owner-occupied. The county has 235,057 total housing units, 5.2% of which are vacant.
The largest employment sector in New Castle County, Delaware is professional, scientific, and management services, employing 25.2% of workers. The unemployment rate is 3.2%.
Wilmington is among the largest cities associated with New Castle County, Delaware, with a population of 71,124.
New Castle County, DE Climate
New Castle County, DE has an average annual temperature of 12.5°C (55°F) and receives about 1144 mm of precipitation per year. The warmest month is July and the coldest is January. Figures are 1970–2000 climate normals.
12.5°C
Avg Temp
1144
Precip (mm/yr)
Jul
Hottest Month
Jan
Coldest Month
| Month | Avg (°C/°F) | Precip |
|---|---|---|
| January | 0° / 32° | 90 mm |
| February | 1° / 34° | 72 mm |
| March | 6° / 43° | 103 mm |
| April | 11° / 52° | 92 mm |
| May | 17° / 62° | 108 mm |
| June | 22° / 71° | 99 mm |
| July | 25° / 76° | 112 mm |
| August | 24° / 75° | 102 mm |
| September | 20° / 68° | 106 mm |
| October | 14° / 56° | 84 mm |
| November | 8° / 47° | 85 mm |
| December | 3° / 38° | 91 mm |
1970–2000 normals from WorldClim 2.1 (~9 km grid). Precipitation can be less precise near mountains or coastlines, where rainfall varies sharply over short distances.
Best time to visit New Castle County, DE
The most comfortable months to visit New Castle County, DE are typically June, September and August, when temperatures are mildest and rainfall is relatively low. The hottest month is July (around 30°C high). The coldest is January (near -4°C low). July is usually the wettest month.
Where to stay near New Castle County
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Data from the American Community Survey (ACS) 5-Year estimates.
Source: U.S. Census Bureau ACS, 2026.