State Trunk Highway 42 is a state highway in the U.S. state of Wisconsin. It runs for 135 miles (217 km) north–south in northeast Wisconsin from Sheboygan to the ferry dock in Northport. Much of the highway is part of the Lake Michigan Circle Tour from the eastern junction with U.S. Highway 10 (US 10) in Manitowoc to its junction with WIS 57 in Sister Bay. WIS 42 parallels I-43 from Sheboygan to Manitowoc, and parallels WIS 57 throughout much of the route, particularly from Manitowoc to Sturgeon Bay, meeting the northern terminus of WIS 57 in Sister Bay.