Sangamon County, Illinois

Founding: 1821
Parent counties: Bond and Madison

Namesake: The Sangamon River
Seat: Springfield (1821–)

Land area: 868 square miles

Population (2020): 196,343

Population (historic): 12,960 (1830); 19,228 (1850); 46,352 (1870); 71,593 (1900); 111,733 (1930)

Periods of population growth: pre-1830–2010

Subdivisions: Four cities; 23 villages; 26 townships

Pre-1940 residences (estimated): 15,027 (16.3%)
Pre-1940 housing survival rate: 44.9%
Pre-1860 housing survival rate (1940): 10.6%

Farm housing in disrepair (1950): 5.6%

Nonfarm housing in disrepair (1950): 5.4%

Average farmhouse value (1930): $2,048
Average outbuilding value (1930): $1,671

Average farmhouse size (1940): 5.8 rooms
Number of farms (1920): 3,425
Average farm size (1920): 134.7 acres
Sources of settlement: Kentucky, Ohio, Ireland, Germany, New York, Virginia, and Pennsylvania
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Springfield

Namesake: A traditional name

Founding: 1821 (platting); 1828 (post office); 1840 (incorporation)

Population (2020): 114,394

Population (historic): 2,579 (1840); 9,320 (1860); 19,743 (1880); 34,159 (1900); 71,864 (1930)

Periods of population growth: pre-1840–2010
Pre-1940 residences (estimated): 9,958 (18.2%)
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