Wisconsin State Trunk Highway System

Wisconsin State Trunk Highway System
Highway markers for Interstate 94, U.S. Highway 12 and WIS 35
System information
Maintained by WisDOT
Length:	11,753 mi (18,915 km)
Formed:	1918
Highway names
Interstates:	Interstate n (I-n)
US Highways:	U.S. Highway n (US n)
State:	(State Trunk) Highway n (STH-n or WIS n)
System links
Wisconsin State Trunk Highway System Interstate U.S. State Scenic Rustic

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 Transportation (WisDOT).

The state of Wisconsin is served by eight Interstate Highways, consisting of five primary routes and three auxiliary routes. The first part of this system was constructed in 1956, and its most recent expansion took place in 2015, with the addition of I-41 to the system. Wisconsin's longest interstate highway is I-94, at 348 miles, and its shortest is I-535, which extends only 1.2 miles into the state.

There are also fourteen United States Numbered Highways in the state of Wisconsin, which were designated beginning in 1926 and ending in the mid-1930s. The routes of the U.S. highway system in Wisconsin have remained essentially unchanged since U.S. Route 110 was downgraded to a state highway in 1939. There are also several business routes, usually maintained by local governments.