Des Moines was founded in May 1843 when Captain James Allen built a fort on the site where the Des Moines and Raccoon Rivers merge. Allen wanted to use the name Fort Raccoon, however the U.S. War Department told him to name it Fort Des Moines. The origin of the name Des Moines is uncertain. The French "Des Moines" translates literally to "Of The Monks." "Rivière Des Moines" translates to "river of the monks," known today under the anglicized name of Des Moines River. It could have referred to the river of the Moingonas, named after an Indian tribe that resided in the area and built burial mounds. Others see it as referring to French Trappist monks while some of whom lived in huts at the mouth of the river.A more recent theory uses a study of Miami-Illinois tribal names to say the word Moingoana, one of the names given to region, comes from word mooyiinkweena, a derogatory name which translates roughly to "the excrement-faces." The name was seemly given to Marquette and Jolliet by a tribal leader in order to dissuade them from doing busy with a neighboring tribe.

Settlers came and lived near the fort, and on May 25, 1846, Fort Des Moines became the seat of Polk County. On September 22, 1851, it was incorporated as a city with its own charter approved in a vote on October 18. In 1857, the name Fort Des Moines was shortened to Des Moines alone and the state capital was moved from Iowa City. By 1900, Des Moines was Iowa's largest city with a population of 62,139.