Rock Island County, Illinois

Founding: 1833 (declared in 1831)
Parent county: Jo Daviess

Namesake: Rock Island
Seat: Rock Island (1835–)

Land area: 428 square miles

Population (2020): 144,672

Population (historic): 2,610 (1840); 21,005 (1860); 38,302 (1880); 55,249 (1900); 98,191 (1930)

Periods of population growth: pre-1840–1970; 1990s

Subdivisions: Four cities; 11 villages; two CDPs; 18 townships

National Register listings: 32

Pre-1940 residences (estimated): 16,895 (25.6%)
Pre-1940 housing survival rate: 51.8%
Pre-1860 housing survival rate (1940): 16.4%

Farm housing in disrepair (1950): 7.9%

Nonfarm housing in disrepair (1950): 4.3%

Average farmhouse value (1930): $2,428
Average outbuilding value (1930): $2,171

Average farmhouse size (1940): 6.3 rooms
Number of farms (1920): 2,045
Average farm size (1920): 87.3 acres
Sources of settlement: Germany, Pennsylvania, New York, Ohio, and Sweden
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Rock Island

Namesake: Rock Island

Founding: 1835 (platting as Stephenson); 1835 (post office); 1841 (incorporation)

Population (2020): 37,108

Population (historic): 1,711 (1850); 7,890 (1870); 13,634 (1890); 24,335 (1910); 37,953 (1930)

Periods of population growth: pre-1850–1960
Pre-1940 residences (estimated): 6,682 (38.2%)
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Outstanding Buildings

1. William Mill House (c. 1855). 13525 303rd Road. Canoe Creek. Greek Revival.
2. Jerome Caldwell Farm (c. 1880). 14015 Knoxville Road. Rural. Second Empire.