Black Hawk County, IA
Black Hawk County was created from parts of Buchanan county in 1853. It spans an area of 573 mi² and is located in eastern Iowa. It is the fifth most populous county in the state, with a population of 132,408 as of 2018. The Cedar Rivers almost exactly down the county's middle. Black Hawk was named after a Sauk military leader from the Black Hawk War of 1832.
Johnson County, IA
Johnson County covers an area of 623 mi² and is found in eastern Iowa. It was named for the 9th U.S. President, Richard Johnson. The fourth most populous county in the state, Johnson County is home to 151,260 residents. The county was established in 1838 and the county seat is currently located in Iowa City.
Linn County, IA
Linn County covers an area of 725 mi² and was named after Missouri Senator Lewis F. Linn. Found in eastern Iowa, it is the second most populous county and has a population of 225,909. The county seat is currently located in Cedar Rapids. Established in 1837, Linn County grew fairly slowly until the first rail line was built through Cedar Rapids in 1859.
Polk County, IA
Named for former U.S. President James K. Polk, Polk County was established in 1845. It covers an area of 592 mi² and is located in central Iowa. With a population of 487,204, it is the most populous county in the state. The county seat, Des Moines, is as also the state capital.
Scott County, IA
Scott County covers an area of 468 mi² and is found in eastern Iowa. It is the third most populous county in the state. Scott County was established in 1837, and experiences an average of 37 inches of rain, 28 inches of snow and 203 days of sunshine per year. The county seat is currently located in Davenport.