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Johnson County, Iowa facts for kids

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Johnson County
Johnson County Courthouse
Official seal of Johnson County
Map of Iowa highlighting Johnson County
Location within the U.S. state of Iowa
Map of the United States highlighting Iowa
Iowa's location within the U.S.
Country  United States
State  Iowa
Founded December 21, 1837
Named for Richard Mentor Johnson (1837–2020)
Lulu Johnson (since 2020)
Seat Iowa City
Largest city Iowa City
 • Total 623 sq mi (1,610 km2)
 • Land 614 sq mi (1,590 km2)
 • Water 9.1 sq mi (24 km2)  1.5%
 • Total 152,854
 • Density 245.35/sq mi (94.73/km2)
Time zone UTC−6 (Central)
 • Summer (DST) UTC−5 (CDT)
Congressional district 2nd

Johnson County is located in the U.S. state of Iowa. As of the 2020 census, the population was 152,854, making it the fourth-most populous county in Iowa. The county seat is Iowa City, home of the University of Iowa.

Johnson County is included in the Iowa City metropolitan area, which is also included in the Cedar Rapids-Iowa City Corridor Combined Statistical Area.


Johnson County was created on December 21, 1837 by the legislature of the Wisconsin Territory. The county was carved out of territory formerly in Dubuque County, and was not initially provided with a civil government, instead being governed by Cedar County officials. It was named for the US Vice President Richard M. Johnson.

The first courthouse in the county was a two story log cabin structure, built in 1838 in the town of Napoleon, about two miles south of the current courthouse. The building stood across from what later would become the James McCollister Farmstead on land later owned by Philip Clark.

Old Johnson Cty Courthouse
Old Johnson County Courthouse, Iowa City, 1857-1899

After Iowa City was established by fiat as the new territorial capitol of Iowa, the county seat was removed there. The second Johnson County Courthouse, the first in Iowa City, was built on Lot 8 Block 8 of the County Seat Addition to Iowa City in 1842 for $3,690. This location was in the southeast corner of the intersection of Harrison and Clinton Streets. The building was intended to be 56 x 28 feet and two stories tall. The building was built by James Trimble, who had previously built the first jail.

A third courthouse was built in 1857 in the courthouse square located on Clinton Street between Court and Harrison Streets. It was used until it was found to be dangerous due to cracks in the south wall in 1899. The building was apparently built of brick with stone and wood ornamentation.

The Richardsonian Romanesque style courthouse in use today was designed by the firm of Rush, Bowman and Rush of Grand Rapids, MI. It was bid at a cost of $111,000 and built by the firm Rowson and Son of Johnson County. The cornerstone was laid in December 1899. The building's tower was based on Henry Hobson Richardson's design for the spire of Trinity Church in Boston. The building was dedicated on June 8, 1901. The currently unused jail that stands to the west of the courthouse was designed by C.L. Wundt of Burlington on behalf of the Stewart Iron Works, Cleveland, OH and bid for $14,000.


According to the U.S. Census Bureau, the county has a total area of 623 square miles (1,610 km2), of which 614 square miles (1,590 km2) is land and 9.1 square miles (24 km2) (1.5%) is water.

Major highways

  • I-80.svg Interstate 80
  • I-380 (IA).svg Interstate 380
  • US 6.svg U.S. Highway 6
  • US 218 (IA).svg U.S. Highway 218
  • Iowa 1.svg Iowa Highway 1
  • Iowa 22.svg Iowa Highway 22
  • Iowa 27.svg Iowa Highway 27

Adjacent counties


Historical population
Census Pop.
1850 4,472
1860 17,573 293.0%
1870 24,898 41.7%
1880 25,429 2.1%
1890 23,082 −9.2%
1900 24,817 7.5%
1910 25,914 4.4%
1920 26,462 2.1%
1930 30,276 14.4%
1940 33,191 9.6%
1950 45,756 37.9%
1960 53,663 17.3%
1970 72,127 34.4%
1980 81,717 13.3%
1990 96,119 17.6%
2000 111,006 15.5%
2010 130,882 17.9%
2020 152,854 16.8%
U.S. Decennial Census
1790-1960 1900-1990
1990-2000 2010-2019
Population of Johnson County from US census data

2020 census

The 2020 census recorded a population of 152,854 in the county, with a population density of 245.8946/sq mi (94.9404/km2). 93.62% of the population reported being of one race. 69.93% were non-Hispanic White, 8.40% were Black, 6.67% were Hispanic, 0.21% were Native American, 5.63% were Asian, 0.03% were Native Hawaiian or Pacific Islander and 9.13% were some other race or more than one race. There were 65,916 housing units, of which 61,335 were occupied.

2010 census

The 2010 census recorded a population of 130,882 in the county, with a population density of 212.9964/sq mi (82.2384/km2). There were 55,967 housing units, of which 52,715 were occupied.



Census-designated place

Other unincorporated communities

Ghost towns


  • Big Grove Township
  • Cedar Township
  • Clear Creek Township
  • East Lucas Township
  • Fremont Township
  • Graham Township
  • Hardin Township
  • Jefferson Township
  • Liberty Township
  • Lincoln Township
  • Madison Township
  • Monroe Township
  • Newport Township
  • Oxford Township
  • Penn Township
  • Pleasant Valley Township
  • Scott Township
  • Sharon Township
  • Union Township
  • Washington Township

Population ranking

The population ranking of the following table is based on the 2010 census of Johnson County.

county seat

Rank City/Town/etc. Municipal type Population (2010 Census)
1 Iowa City City 67,862
2 Coralville City 18,907
3 North Liberty City 13,374
4 West Branch (mostly in Cedar County) City 2,322
5 Solon City 2,037
6 Tiffin City 1,947
7 Lone Tree City 1,300
8 University Heights City 1,051
9 Swisher City 879
10 Oxford City 807
11 Hills City 703
12 Shueyville City 577
13 Frytown CDP 165

Notable natives

  • John T. Struble (1831–1916) early builder and farmer.
  • Grant Wood, artist.

See also

Kids robot.svg In Spanish: Condado de Johnson (Iowa) para niños

Black History Month on Kiddle
Distinguished African-American Artists:
Sharif Bey
Hale Woodruff
Richmond Barthé
Purvis Young
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