Mercer County, Pennsylvania

Founding: 1803 (declared in 1800)
Parent county: Allegheny

Namesake: Hugh Mercer, Continental Army general
Seat: Mercer (1804–)

Land area: 673 square miles

Population (2020): 110,652

Population (historic): 3,228 (1800); 32,873 (1840); 49,977 (1870); 57,387 (1900); 99,246 (1930)

Periods of population growth: pre-1800–1880; 1890–1960

Subdivisions: Three cities; 14 boroughs; two CDPs; 31 townships

National Register listings: 15

Pre-1940 residences (estimated): 13,885 (26.6%)
Pre-1940 housing survival rate: 60.2%
Pre-1860 housing survival rate (1940): 17.7%

Farm housing in disrepair (1950): 11.6%

Nonfarm housing in disrepair (1950): 6.2%
Average farmhouse value (1930): $1,847
Average outbuilding value (1930): $1,470
Average farmhouse size (1940): 6.8 rooms
Number of farms (1920): 4,499
Average farm size (1920): 54.6 acres
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Mercer

Namesake: Hugh Mercer, Continental Army general

Founding: 1803 (platting); 1805 (post office); 1814 (incorporation)

Population (2020): 1,982

Population (historic): 781 (1840); 1,249 (1860); 2,344 (1880); 1,804 (1900); 2,125 (1930)

Periods of population growth: pre-1840–1860; 1870s; 1900s; 1920–1960
Pre-1940 residences (estimated): 401 (41.3%)
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Outstanding Buildings

1. House (c. 1885). 148 Cribbs Road. Findley. Italianate/Eastlake.
2. Mount Hickory / James Pierce Farm (c. 1865). 1202 Keel Ridge Road. Hickory. Italianate.
3. *Locust Grove / Robert Stewart House (c. 1870). 5465 East State Street. Hickory. Italianate.
4. Robert Fruit House (c. 1830). 1702 Lake Road. Jefferson. Federal.
5. Samuel Sample Farm (c. 1865). 2305 Mercer–West Middlesex Road. Lackawannock. Italianate.
6. James Carnahan Farm (c. 1835). 307 Roberts Road. Mill Creek. Federal.
7. Keystone Farm / David Frampton Farm (c. 1870). 236 Shenango Park Road. Pymatuning. Italianate.
8. William Geibner Farm (c. 1865). 2760 Sandy Lake–Grove City Road. Sandy Lake.
9. Stephen Bell House (c. 1875). 134 Mitchell Road. Shenango. Italianate.
10. *Arthur Johnston House (1831). 1553 Perry Highway. Springfield. Federal.
11. *William Porter House (c. 1890). 264 Porter Road. West Salem. Queen Anne/Italianate.
12. House (c. 1865). 25 Sharon Road. West Salem. Italianate.