This is a list of the ninety-nine counties in the U.S. state of Iowa. The first two counties, Des Moines County an Dubuque County, were created in 1834 when Iowa was part of the Michigan Territory. Counties continued to be created by the state government until 1857, when the last county, Humboldt County, was created. One of the most significant days in Iowa county history was January 15, 1851, on which 49 counties were created.