The site for a courthouse west of the Des Moines River was purchased by Polk County in 1846. Because of the offset of the city's grid along Fifth Street, the courthouse site served as the termination of the eastern portion of Court Street. Two years after the site was acquired, the first courthouse was built—an unpretentious two-story building with a brick veneer. This plain, simple structure was replaced by a far more opulent masonry building designed by Dyer H. Young. Construction of this second building started in 1858, but it was not occupied by the courts until 1866. In style this second courthouse was French Second Empire; it was surmounted by a tall, spirelike, segmented dome and lantern.

To accommodate the expanded needs of county government, the third and present courthouse was built in what was labeled as “a modified Renaissance style,” i.e., Beaux-Arts Classical. In general the design of the building is sophisticated and correct; it has a multifloor central rotunda and a gray limestone facade articulated by a rusticated base and rows of pilasters above. Externally, its most unusual feature is its 116-foot-high central tower with large clock faces and the wonderful array of 28 sculptured masks found in the keystones of the arched second-floor windows. Within, around the fourth level of the central rotunda, is an impressive group of murals. These are: The Indian in His Natural State, by Bert Phillips; The Coming of the White Men, by Douglas Volk; The Departure of the Indians from Iowa, by Charles A. Cumming; and Presenting the Flag, by Edward Simmons. In 1985 restoration of the building was carried out by Bussard/Divas and Sven Paulsen.