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New Castle County
County of New Castle
Old New Castle Courthouse in New Castle (1936)
Old New Castle Courthouse in New Castle (1936)
Flag of New Castle County
Official seal of New Castle County
Map of Delaware highlighting New Castle County
Location within the U.S. state of Delaware
Map of the United States highlighting Delaware
Delaware's location within the U.S.
Country  United States
State  Delaware
Founded August 8, 1637
Named for William Cavendish, 1st Duke of Newcastle
Seat Wilmington
Largest city Wilmington
 • Total 494 sq mi (1,280 km2)
 • Land 426 sq mi (1,100 km2)
 • Water 68 sq mi (180 km2)  13.8%
 • Total 570,719
 • Estimate 
 • Density 1,155.3/sq mi (446.1/km2)
Time zone UTC−5 (Eastern)
 • Summer (DST) UTC−4 (EDT)
Congressional district At-large

New Castle County is the northernmost of the three counties of the U.S. state of Delaware. As of the 2020 census, the population was 570,719, making it the most populous county in Delaware, with just under 60% of the state's population of 989,948. The county seat is Wilmington, which is also the state's most populous city.

New Castle County is included in the Philadelphia-Camden-Wilmington, PA-NJ-DE-MD Metropolitan Statistical Area. The county is named after William Cavendish, 1st Duke of Newcastle (c. 1593–1676).

New Castle County has the highest population and population density of any Delaware county, and it is the smallest county in the state by area. It has more people than the other two counties, Kent and Sussex, combined. It is also the most economically developed of the three.

New Castle County is home to two minor league sports teams: the Wilmington Blue Rocks (baseball) and the Delaware Blue Coats (basketball), both of which play in Wilmington. It also has a professional auto racing track in New Castle known as Airport Speedway, with races on Saturday nights throughout the summer.


The first permanent European settlement on Delaware soil was Fort Christina, resulting from Peter Minuit's 1638 expedition on the Swedish vessels Fogel Grip and Kalmar Nyckel. The Swedes laid out the town at the site of modern-day Wilmington. They contracted with the Lenape Native Americans for land of Old Cape Henlopen north to Sankikans (Trenton Falls), and inland as far as they desired. However, a dispute ensued between the Swedes and the Dutch, who asserted a prior claim to that land.

In 1640, New Sweden was founded a few miles south of Christina. In 1644, Queen Christina appointed Lt. Col. Johan Printz as Governor of New Sweden. She directed boundaries to be set and to reach Cape Henlopen north along the west side of Godyn's Bay (Delaware Bay), up the South River (Delaware River), past Minquas Kill (Christina River), to Sankikans (Trenton Falls). Printz settled on Tinicum Island, as the seat of government and capital of the New Sweden colony.

Peter Stuyvesant, Governor of New Netherland, sailed up the South River in 1651. He purchased land from the Lenape that covered Minquas Kill to Bompties Hook (Bombay Hook); the Lenape had sold part of the property to the Swedes in 1638. Stuyvesant began to build Fort Casimir (contemporary New Castle).

In 1654, Johan Risingh, Commissary and Councilor to the Governor Lt. Col. Printz, officially assumed Printz's duties and began to expel all Dutch from New Sweden. Fort Casimir surrendered and was renamed Fort Trinity in 1654. The Swedes had complete possession of the west side of the Delaware River. On June 21, 1654, the Lenape met with the Swedes to reaffirm the purchase.

Having learned of the fall of Fort Casimir, the Dutch sent Stuyvesant to drive the Swedes from both sides of the river. They allowed only Dutch colonists to settle in the area and on August 31, 1655, the territory was converted back to Fort Casimir. Consequently, Fort Christina fell on September 15 to the Dutch and New Netherland ruled once again. John Paul Jacquet was immediately appointed Governor, making New Amstel the capital of the Dutch-controlled colony.

As payment[to whom?] for regaining the territory, the Dutch West India Company conveyed land from the south side of Christina Kill to Bombay Hook, and as far west as Minquas land. This land was known as the Colony of The City. On December 22, 1663, the Dutch transferred property rights to the territory along the Delaware River to England.

In 1664, the Duke of York, James, was granted this land by King Charles II. One of the first acts by the Duke was to order removal of all Dutch from New Amsterdam; he renamed New Amstel as New Castle. In 1672, the town of New Castle was incorporated and English law ordered. However, in 1673, the Dutch attacked the territory, reclaiming it for their own.

On September 12, 1673, the Dutch established New Amstel in present-day Delaware, fairly coterminous with today's New Castle County. The establishment was not stable, and it was transferred to the British under the Treaty of Westminster on February 9, 1674. On November 6, 1674, New Amstel was made dependent on New York Colony, and was renamed New Castle on November 11, 1674.

On September 22, 1676, New Castle County was formally placed under the Duke of York's laws. It gained land from Upland County on November 12, 1678.

On June 21, 1680, St. Jones County was carved from New Castle County. It is known today as Kent County, Delaware. On August 24, 1682, New Castle County, along with the rest of the surrounding land, was transferred from the Colony of New York to the possession of William Penn, who established the Colony of Delaware.

In September 1673, a Dutch council established a court at New Castle with the boundaries defined as north of Steen Kill (present-day Stoney Creek) and south to Bomties Hook (renamed Bombay Hook). In 1681, a 12-mile arc was drawn to specifically delineate the northern border of New Castle County as it currently exists. In 1685, the western border was finally established by King James II; this was set as a line from Old Cape Henlopen (presently Fenwick) west to the middle of the peninsula and north up to the middle of the peninsula to the 40th parallel.


Chesapeake and Delaware Canal eastern entrance
Chesapeake and Delaware Canal

According to the U.S. Census Bureau, the county has a total area of 494 square miles (1,280 km2), of which 426 square miles (1,100 km2) is land and 68 square miles (180 km2) (13.8%) is water. The boundaries of New Castle County are described in § 102 of the Delaware Code. The county is drained by Brandywine Creek, Christina River, and other channels. Its eastern edge sits along the Delaware River and Delaware Bay.

Two small exclaves of the county and the state lie across the Delaware River, on its east bank on the New Jersey side, Finns Point adjacent to Pennsville Township, New Jersey, and the northern tip of Artificial Island, adjacent to Lower Alloways Creek Township, New Jersey.

New Castle County, like all of Delaware's counties, is subdivided into Hundreds. New Castle County is apportioned into ten Hundreds: Brandywine, Christiana, Wilmington (the city of Wilmington, which, by law, is a Hundred in itself), Mill Creek, White Clay Creek, Pencader, New Castle, Red Lion, St. Georges and Appoquinimink.

The highest natural point in Delaware, Ebright Azimuth at 451 feet (137 m), is located in New Castle County.

The Chesapeake and Delaware Canal was built through New Castle County, and adjoining Cecil County, Maryland, between 1822 and 1829.

Adjacent counties

Major Highways

  • I-95
  • I-95 / Delaware Turnpike
  • I-295 / US 40 / Delaware Turnpike (Delaware Memorial Bridge)
  • I-495
  • US 13

  • US 13 Bus.
  • US 40
  • US 202
  • US 301
  • DE 1
  • DE 2
  • DE 3
  • DE 4
  • DE 7
  • DE 9
  • DE 9A
  • DE 41
  • DE 52
  • DE 71
  • DE 72
  • DE 82
  • DE 100
  • DE 141
  • DE 202
  • DE 273
  • DE 282
  • DE 896


Historical population
Census Pop.
1790 19,688
1800 25,361 28.8%
1810 24,429 −3.7%
1820 27,899 14.2%
1830 29,720 6.5%
1840 33,120 11.4%
1850 42,780 29.2%
1860 54,797 28.1%
1870 63,515 15.9%
1880 77,716 22.4%
1890 97,182 25.0%
1900 109,697 12.9%
1910 123,188 12.3%
1920 148,239 20.3%
1930 161,032 8.6%
1940 179,562 11.5%
1950 218,879 21.9%
1960 307,446 40.5%
1970 385,856 25.5%
1980 398,115 3.2%
1990 441,946 11.0%
2000 500,265 13.2%
2010 538,479 7.6%
2020 570,719 6.0%
2021 (est.) 570,719 6.0%
U.S. Decennial Census
1790-1960 1900-1990
1990-2000 2010-2020
Hindu Temple Delaware Pic -2
Hindu Temple of Delaware

2010 census

As of the 2010 census, there were 538,479 people, 202,651 households, and 134,743 families residing in the county. The population density was 1,263.2 inhabitants per square mile (487.7/km2). There were 217,511 housing units at an average density of 510.2 per square mile (197.0/km2). The racial makeup of the county was 65.5% white, 23.7% black or African American, 4.3% Asian, 0.3% American Indian, 3.5% from other races, and 2.5% from two or more races. Those of Hispanic or Latino origin made up 8.7% of the population. In terms of ancestry, 19.2% were Irish, 15.0% were German, 11.7% were Italian, 11.3% were English, 6.2% were Polish, and 3.0% were American.

Of the 202,651 households, 33.8% had children under the age of 18 living with them, 46.6% were married couples living together, 14.9% had a female householder with no husband present, 33.5% were non-families, and 26.1% of all households were made up of individuals. The average household size was 2.57 and the average family size was 3.11. The median age was 37.2 years.

The median income for a household in the county was $62,474 and the median income for a family was $78,072. Males had a median income of $52,637 versus $41,693 for females. The per capita income for the county was $31,220. About 6.6% of families and 10.3% of the population were below the poverty line, including 13.6% of those under age 18 and 7.6% of those age 65 or over.


Wilmington Delaware skyline
Newark Delaware
Middletown DE




Census-designated places

Unincorporated communities

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