Rock County, Wisconsin

Founding: 1839 (declared in 1836)
Parent county: Milwaukee
Namesake: The Rock River
Seat: Janesville (1839–)
Land area: 718 square miles
Population (2020): 163,687
Population (historic): 1,701 (1840); 36,690 (1860); 38,823 (1880); 51,203 (1900); 74,206 (1930)
Periods of population growth: pre-1840–1870; 1880–2020
Subdivisions: Five cities; three villages; one CDP; 20 towns
Pre-1940 residences (estimated): 14,265 (20.2%)
Pre-1940 housing survival rate: 70.1%
Pre-1860 housing survival rate (1940): 14.4%

Farm housing in disrepair (1950): 4.6%

Average farmhouse value (1930): $2,243
Average outbuilding value (1930): $2,784

Average farmhouse size (1940): 7.1 rooms

Number of farms (1920): 3,660
Average farm size (1920): 93.8 acres
Sources of settlement: New York, Ireland, Germany, Norway, England, and New England
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Janesville

 
Namesake: Henry Janes, platter
Founding: 1835 (platting); 1837 (post office); 1853 (incorporation)
Population (2020): 65,615
Population (historic): 7,703 (1860); 9,018 (1880); 13,185 (1900); 21,628 (1930)
Periods of population growth: pre-1860–2020
Pre-1940 residences (estimated): 4,848 (16.8%)
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