Mahaska County, Iowa

 

Founding: 1844 (declared in 1843)
Parent counties: Keokuk and unorganized territory

Namesake: Mahaska, Iowa chief
Seat: Oskaloosa (1844–)

Land area: 571 square miles

Population (2020): 22,190

Population (historic): 5,989 (1850); 22,508 (1870); 28,805 (1890); 29,860 (1910); 25,804 (1930)

Periods of population growth: pre-1850–1900; 1930s; 1970s; 1990–2010

Subdivisions: Ten cities; 18 townships

National Register listings: 49

Pre-1940 residences (estimated): 3,552 (36%)
Pre-1940 housing survival rate: 44.8%
Pre-1860 housing survival rate (1940): 8.8%

Farm housing in disrepair (1950): 5.3%

Nonfarm housing in disrepair (1950): 6.4%

Average farmhouse value (1930): $2,139
Average outbuilding value (1930): $2,026
Average farmhouse size (1940): 6.4 rooms
Number of farms (1920): 2,784
Average farm size (1920): 105.5 acres
Sources of settlement: Ohio, Illinois, Pennsylvania, Indiana, New York, Missouri, Virginia, and Kentucky
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Oskaloosa

Namesake: Uncertain—perhaps a mythical Creek figure

Founding: 1844 (platting); 1844 (post office); 1853 (incorporation)

Population (2020): 11,558

Population (historic): 625 (1850); 3,204 (1870); 6,558 (1890); 9,466 (1910); 10,123 (1930)

Periods of population growth: 1844–1860; 1870–1910; 1920–1950; 1960s; 1990–2020
Pre-1940 residences (estimated): 1,939 (35.8%)
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Outstanding Buildings

1. *John Vorhees Farm (1871). 1261 185th Road. Black Oak. Italianate.
2. *Maas Van Donselaar Farm (c. 1875). 1825 Barrows Road. Black Oak. Italianate.
3. *Anna Van Donselaar Farm (c. 1870). 1051 State Route 163. Black Oak. Italianate.
4. *Daniel Nelson Farm (1853). 2211 Nelson Lane. Spring Creek.