Rochester was selected as the first county seat in 1838, but the governor refused to approve the act. Subsequently, a committee chose Keosauqua as the county seat and the governor approved this choice. A two-story brick courthouse completed in 1843. It is still in use today and is the oldest courthouse in Iowa. The framework is made of oak, which was strengthened by installing truss rods through the building. The style of architecture is Greek Revival. The solid brick walls are 22 inches thick on the first flood and 18 inches thick on the second.
For many years, the courtroom on the second floor was hailed as the largest auditorium unbroken by columns or pillars in Iowa. The interior is decorated with framed pictures of judges, old maps, and other historical memorabilia. Native walnut woodwork also accents the inside.