On July 19, 1852, a contract was made for a courthouse to be built in Marietta, the first county seat. It was 32 by 22 feet and just one-story high. However, the citizens of Marshall (now Marshalltown) wanted the county seat to be moved there, so they built a courthouse of their own. The one in Marietta was sold later for $175.
The courthouse in Marshall was considered to be very large at 40 by 60 feet. It was two stories high and made of brick with a stone foundation. This courthouse was used from 1860 to 1886. By the middle of the 1870's it was in poor condition. However, a new courthouse was not approved by voters until 1883.
The third and present courthouse was completed in 1886, in Classic-Revival style. The limestone structure has a tower and clock that reaches 175 into the sky. The building underwent renovations in 1975 and is listed on the National Register of Historic Places.