New Castle County, Delaware

Founding: 1673
Parent county: Unorganized territory
Namesake: The city of New Castle
Seat: New Castle (1664–1881); Wilmington (1881–)
Land area: 426 square miles
Population (2020): 570,719
Population (historic): 19,688 (1790); 33,120 (1840); 63,515 (1870); 109,697 (1900); 161,032 (1930)
Periods of population growth: pre-1790–1800; 1810–2020

Subdivisions: Four cities; six towns; three villages; 13 CDPs
Pre-1940 residences (estimated): 26,905 (11.9%)
Pre-1940 housing survival rate: 50.8%
Pre-1860 housing survival rate (1940): 26.1%

Farm housing in disrepair (1950): 4.3%

Nonfarm housing in disrepair (1950): 4%

Average farmhouse value (1930): $3,988
Average outbuilding value (1930): $4,124

Average farmhouse size (1940): 7.2 rooms

Number of farms (1920): 1,825
Average farm size (1920): 88.9 acres

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New Castle (ex-seat)

 
Namesake: William Cavendish, First Duke of Newcastle
Founding: 1655 (founding as Nieuw Amstel); 1794 (post office)
Population (2020): 5,551
Population (historic): 1,202 (1850); 1,916 (1870); 4,010 (1890); 3,351 (1910); 4,131 (1930)
Periods of population growth: pre-1850–1890; 1910–1950; 1960–1980; 1990–2020

Pre-1940 residences (estimated): 864 (31.7%)
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Wilmington

 
Namesake: Spencer Compton, First Earl of Wilmington
Founding: 1730 (platting as Willingtown); 1731 (incorporation)
Population (2020): 70,898
Population (historic): 5,268 (1820); 13,979 (1850); 30,841 (1870); 76,508 (1900); 106,597 (1930)
Periods of population growth: pre-1820–1920; 1930s; 1980–2000; 2010s

Pre-1940 residences (estimated): 17,195 (48.5%)
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