St. Louis County, Missouri

Founding: 1812
Parent county: Unorganized territory

Namesake: The city of St. Louis
Seat: St. Louis (1812–1877); Clayton (1877–)

Land area: 508 square miles

Population (2020): 1,004,125

Population (historic): 10,049 (1820); 104,978 (1850); 351,189 (1870); 50,040 (1900); 211,593 (1930)

Periods of population growth: pre-1820–1870; 1880–1970

Subdivisions: 70 cities; 18 villages; ten CDPs

Pre-1940 residences (estimated): 42,830 (9.7%)
Pre-1940 housing survival rate: 52.6%
Pre-1860 housing survival rate (1940): 15.2%

Farm housing in disrepair (1950): 5.8%

Nonfarm housing in disrepair (1950): 9.5%

Average farmhouse value (1930): $2,767
Average outbuilding value (1930): $1,778

Average farmhouse size (1940): 5 rooms
Number of farms (1920): 3,735
Average farm size (1920): 47.5 acres

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St. Louis (ex-seat)

Namesake: King Louis IX of France

Founding: 1764 (founding); 1804 (post office); 1822 (incorporation)

Population (2020): 301,578

Population (historic): 1,600 (1810); 16,469 (1840); 310,864 (1870); 575,238 (1900); 821,960 (1930)

Periods of population growth: pre-1810–1920
Pre-1940 residences (estimated): 99,367 (56.4%)

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Clayton

Namesake: Ralph Clayton, owner of the city site

Founding: 1877 (platting); 1885 (post office); 1913 (incorporation)

Population (2020): 17,355

Population (historic): 402 (1890); 3,028 (1920); 9,613 (1930)

Periods of population growth: 1877–1950; 2000s
Pre-1940 residences (estimated): 2,889 (46.3%)

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