Nebraska City is a city in Otoe County, Nebraska, United States. The population was 7,228 at the 2000 census. It is the county seat of Otoe County. Nebraska City is home of Arbor Day, the Missouri River Basin Lewis and Clark Center (which focuses on the natural history achievements of the expedition), and the Mayhew Cabin, the only site in the state recognized by the National Park Service as a station on the Underground Railroad. The Park Service includes it as a destination in its Underground Railroad Network to Freedom Program.The Nebraska State Legislature has credited Nebraska City as being the oldest incorporated city in the state, as it was the first approved by a special act of the Nebraska Territorial Legislature in 1855.