The Wisconsin State Trunk Highway System is the state highway system of the U.S. state of Wisconsin, including Wisconsin's segments of the Interstate Highway System and the United States Numbered Highway System, in addition to its other state trunk highways. These separate types of highways are respectively designated with an I-, US, or STH- (or WIS) prefix. The system also includes minor roads designated as Scenic Byways, four routes intended to promote tourism to scenic and historic areas of the state; and as Rustic Roads, lightly-traveled and often unpaved local roads which the state has deemed worthy of preservation and protection. The state highway system, altogether totaling 11,753 miles (18,915 km) across all of Wisconsin's 72 counties, is maintained by the Wisconsin Department of T