Allegheny County, Pennsylvania

Founding: 1788
Parent counties: Washington and Westmoreland

Namesake: The Allegheny River
Seat: Pittsburgh (1788–)

Land area: 730 square miles

Population (2020): 1,250,578

Population (historic): 10,203 (1790); 50,552 (1830); 178,831 (1860); 775,058 (1900); 1,374,410 (1930)

Periods of population growth: pre-1790–1960; 2010s

Pre-1940 residences (estimated): 177,403 (29.7%)
Pre-1940 housing survival rate: 50.9%
Pre-1860 housing survival rate (1940): 26%

Farm housing in disrepair (1950): 12.2%

Nonfarm housing in disrepair (1950): 6.3%
Average farmhouse value (1930): $3,614
Average outbuilding value (1930): $3,089
Average farmhouse size (1940): 5.7 rooms
Number of farms (1920): 3,972
Average farm size (1920): 48.4 acres
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Pittsburgh

Namesake: William Pitt, British politician
Founding: 1784 (platting); 1788 (post office); 1794 (incorporation)

Population (2020): 302,971

Population (historic): 1,565 (1800); 12,568 (1830); 49,221 (1860); 321,616 (1900); 669,817 (1930)

Periods of population growth: pre-1800–1950
Pre-1940 residences (estimated): 80,287 (51.4%)
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