Nebraska City is a city in, and the county seat of, Otoe County, Nebraska, United States. As of the 2010 census, the city population was 7,289.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.Nebraska City is home of Arbor Day, the Missouri River Basin Lewis and Clark Center, and the Mayhew Cabin, the only site in the state recognized by the National Park Service as a station on the Underground Railroad.