Johnson County, Iowa

Founding: 1838 (declared in 1837)
Parent counties: Cook, Dubuque, Muscatine, and unorganized territory

Namesake: Richard Johnson, U.S. vice president
Seat: Napoleon (1838–1839); Iowa City (1839–)

Land area: 614 square miles

Population (2020): 152,854

Population (historic): 4,472 (1850); 24,898 (1870); 23,082 (1890); 25,914 (1910); 30,276 (1930)

Periods of population growth: pre-1850–1880; 1890–2020

Subdivisions: 11 cities; one CDP; 20 townships

Pre-1940 residences (estimated): 7,349 (11.1%)
Pre-1940 housing survival rate: 69.1%
Pre-1860 housing survival rate (1940): 5.3%

Farm housing in disrepair (1950): 2.9%

Nonfarm housing in disrepair (1950): 2.7%

Average farmhouse value (1930): $2,561
Average outbuilding value (1930): $3,078
Average farmhouse size (1940): 6.7 rooms
Number of farms (1920): 2,625
Average farm size (1920): 122.1 acres
Sources of settlement: Czechoslovakia, Ohio, Pennsylvania, Germany, Ireland, and New York
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Iowa City

Namesake: The state of Iowa

Founding: 1839 (platting); 1839 (post office); 1853 (incorporation)

Population (2020): 74,828

Population (historic): 1,250 (1850); 5,914 (1870); 7,016 (1890); 10,091 (1910); 15,340 (1930)

Periods of population growth: 1839–1880; 1890–2020
Pre-1940 residences (estimated): 4,910 (13.5%)
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