State Trunk Highway 15 (STH-15, commonly known as Highway 15 or WIS 15) is a 14.8-mile (23.8 km)state highway in Outagamie County in the US state of Wisconsin that runs east–west and provides a shortcut to Appleton from U.S. Highway 45 (US 45) for travelers inbound from points north and west. Most of WIS 15 was once part of US 45, which was redirected south of New London to bypass Appleton and provide direct access to Oshkosh and points south.