Carroll County, Illinois

Founding: 1839
Parent county: Jo Daviess

Namesake: Charles Carroll, Maryland politician
Seat: Savanna (1839–1843); Mount Carroll (1843–)

Land area: 445 square miles

Population (2020): 15,702

Population (historic): 1,023 (1840); 11,733 (1860); 16,976 (1880); 18,963 (1900); 18,433 (1930)

Periods of population growth: pre-1840–1900; 1910s; 1940–1960; 2010s

Subdivisions: Three cities; four villages; 12 townships

National Register listings: Seven

Pre-1940 residences (estimated): 3,161 (37.4%)
Pre-1940 housing survival rate: 61.9%
Pre-1860 housing survival rate (1940): 10.8%

Farm housing in disrepair (1950): 3.4%

Nonfarm housing in disrepair (1950): 5.3%

Average farmhouse value (1930): $2,258
Average outbuilding value (1930): $3,008

Average farmhouse size (1940): 7.3 rooms
Number of farms (1920): 1,769
Average farm size (1920): 127.1 acres
Sources of settlement: Pennsylvania, Germany, New York, Maryland, and Ireland
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Savanna (ex-seat)

Namesake: Prairies near the city site

Founding: 1828 (platting); 1835 (post office); 1874 (incorporation)

Population (2020): 2,783

Population (historic): 658 (1850); 971 (1870); 3,097 (1890); 3,691 (1910); 5,086 (1930)

Periods of population growth: pre-1850–1920; 1940s
Pre-1940 residences (estimated): 833 (49.4%)

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Mount Carroll

Namesake: Carroll County

Founding: 1841 (platting); 1845 (post office); 1867 (incorporation)

Population (2020): 1,717

Population (historic): 462 (1850); 1,756 (1870); 1,836 (1890); 1,759 (1910); 1,775 (1930)

Periods of population growth: 1841–1900; 1910s; 1930–1970; 1990s
Pre-1940 residences (estimated): 462 (55.6%)
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Outstanding Buildings

1. James Jones House (c. 1855). 27815 Georgetown Road. Cherry Grove–Shannon.
2. *Joseph Steffens House (1843). 30849 Elkhorn Road. Elkhorn Grove.
3. Henry Harnish Farm (c. 1895). 16148 State Route 64. Mount Carroll. Queen Anne.
4. *Alonzo Heath Farm (c. 1845). Telegraph Road, west of Dimont Road. Rock Creek–Lima. Greek Revival. Razed.
5. *Charles Franks Farm (c. 1850). 34431 US Highway 52. Rock Creek–Lima.
6. *Duncan MacKay House (c. 1855). 7824 Oakville Road. Salem. Greek Revival.