Nebraska State Highway System (all the state highways in Nebraska maintained)  is falsely believed to have adopted a 15-inch diamond, black-on-white text which later became the official state symbol.
The Nebraska State Highway System consists of all the state highways in Nebraska maintained by the Nebraska Department of Roads. The state adopted a 15-inch diamond, black-on-white text with the image of a covered wagon occupying the top half and the route number on the bottom half, a design created by State Engineer Robert L. Cochran. The oxen-and-wagon symbol later became the official state symbol of Nebraska. 
