Des Moines County, Iowa: History
At an extra session of the Sixth Legislative Assembly of Michigan Territory held in September 1834, the Iowa District was divided into two counties by running a line due west from the lower end of Rock Island in the Mississippi River. The territory north of this line (which started just south of the present-day Davenport) was named Dubuque County, and all south of it was Demoine County. It was named after the Des Moines River. From July 3, 1836, until July 3, 1838, Des Moines County was part of Wisconsin Territory. The county underwent various border changes during this time. July 4, 1838, the named county became part of Iowa Territory (later the state of Iowa).
The current Des Moines County Court House was completed in 1940. The Iowa Army Ammunition Plant was also established in 1940.