Des Moines is the capital and most populous city in the U.S. state of Iowa. It is named after the Des Moines River, likely derived from the French Rivière des Moines meaning 'River of the Monks'. The city was incorporated in 1851 as Fort Des Moines and shortened to Des Moines in 1857. Its population was 214,133 at the 2020 census. The six-county Des Moines metropolitan area has an estimated 750,000 residents, the largest metropolitan area located entirely in Iowa. It is the county seat of Polk County, with parts south of County Line Road extending into Warren County.