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

National Register listings: 254

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

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