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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Outstanding Buildings

Isaac Walker Log House (c. 1790). 1355 Noblestown Road. Collier.
Woodville / John Neville House (c. 1775/1785). 1375 Washington Pike. Collier.
Bartram Murray House (c. 1845). Butler–Logan Road, north of Murray Hill Road. East Deer. Greek Revival. Razed.
House (1933). 2255 Buena Vista Road. Elizabeth. Tudor Revival.
Joseph Hutchinson Farm (c. 1865). 201 Round Hill Road. Elizabeth. Greek Revival/Italianate.
Joseph Van Kirk Farm (c. 1840). 337 Round Hill Road. Elizabeth. Greek Revival.
Elisha Peairs Farm (c. 1840). 651 Round Hill Road. Elizabeth.
David Allen House (c. 1820). 659 Magnolia Lane. Forward. Federal.
Harmarsville Presbyterian Church (1851). 531 Indianola Road. Harmar. Greek Revival.
Washington Beale House (c. 1860). 2503 Buchanan Street. Harrison. Italianate.
Philip Burtner House (1818–1821). 1650 Burtner Road. Harrison.
Red Gables / Charles Flaccus Estate (c. 1920). 751 Dorseyville Road. Indiana. Tudor Revival.
William Patterson Estate (c. 1910). 100 Old Pine Lane. Indiana. Shingle.
House (c. 1905). 444 High Road. Jefferson. Classical Revival.
Elm Ridge / John Walker House (1867–1870). 1 Breck Drive. Leet. Italianate/Gothic Revival.
Muotas / William Walker Estate (1904–1905/1928). 21 Little Sewickley Creek Road. Leet. Colonial Revival.
Robert McCully Log House. 1744 James Street. Patton.
William Haymaker Log House (c. 1800). 1256 Northwestern Drive. Patton.
Crossroads Presbyterian Church (1896). 2700 Stroschein Road. Patton. Gothic Revival.
Isaac Blackadore House (c. 1865). 1275 Blackadore Avenue. Penn. Italianate.
Edward McLaughlin Log House (c. 1775). 305 Pike Street. Penn.
Elias Davidson House (c. 1820). 9701 Saltsburg Road. Plum.
Union Presbyterian Church (1907). 6165 Steubenville Pike. Robinson. Gothic Revival.
James Stewart Farm (c. 1834). 537 Sangree Road. Ross. Federal. Razed.
Thomas Shaw House (1824/1840s). 1526 Butler Plank Road. Shaler. Greek Revival.
Isaac Lightner House (1833). 2407 Mount Royal Boulevard. Shaler. Greek Revival.
Peter Boyer House (c. 1850). 5679 Library Road. Snowden. Greek Revival.
James Miller House (1808/1830s). 1 Stone Manse Drive. Snowden.
Joseph Phillips House (1806). 170 Seegar Road. Upper St. Clair. Georgian.
John Gilfillan Farm (c. 1850). 1950 Washington Road. Upper St. Clair. Italianate.