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 _________________________________________________________________________________ Pittsburgh Namesake: William Pitt, British pol...