Johnson County

Also known as Johnson County, Iowa, Johnson County, IA

county in Iowa, United States

Key facts

Country: United States
State: Iowa
Founded: December 21, 1837 (created), July 4, 1838 (organized)
Named after: Richard Mentor Johnson (1837–2020), Lulu Johnson (since 2020)
Seat: Iowa City
Largest city: Iowa City
Total: 623.063 sq mi (1,613.73 km )
Land: 612.997 sq mi (1,587.65 km )
Water: 10.066 sq mi (26.07 km ) 1.62%
Estimate 2025: 160,044
Density: 249.355/sq mi (96.2766/km )
Time zone: UTC−6 ( Central )
Summer dst

Article

Johnson County is located in the U.S. state of Iowa. As of the 2020 census, the population was 152,854, and was estimated to be 160,044 in 2025, making it the fourth-most populous county in Iowa. The county seat and the largest city 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.

History