SR 156 is part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration. The route is eligible for the State Scenic Highway System, and from east of Castroville to US 101 is officially designated as a scenic highway by the California Department of Transportation, meaning that it is a substantial section of highway passing through a "memorable landscape" with no "visual intrusions", where the potential designation has gained popular favor with the community.