Neb. Rev. Stat. § 39-857

If any such county, prior to May 21, 1935, has acquired, purchased or received an assignment by gift or otherwise of a franchise or authority of the United States Government to build any highway, wagon, vehicle or automobile bridge within the State of Nebraska and any adjoining state, across any river, navigable or nonnavigable stream, forming a boundary line between any county within the State of Nebraska and any other state of the United States, if in every other way regular in form, the same shall be and is hereby declared legal and valid and binding on the county, and of the same force and effect as if authority had been theretofore directly conferred on the county.