I·o·wa 2 (ī'ə-wə) A state of the north-central United States. It was admitted as the 29th state in 1846. Part of the Louisiana Purchase of 1803, Iowa was organized as a separate territory in 1838. The Mound Builders lived in the area in prehistoric times. Des Moines is the capital and the largest city. Population: 2,990,000. I'o·wan adj.