Headwaters Wilderness spans 22,033 acres in northeastern Wisconsin within the Nicolet unit of the Chequamegon–Nicolet National Forest and is the largest federally designated wilderness area on the state’s mainland. It protects the headwaters of the Pine River, a legally protected wild river flowing to the Menominee River, across a landscape of forested swampland, bog, pine stands, and some northern hardwoods. The Shelp Lake unit contains some of the national forest’s largest and oldest trees, and primitive trails pass old-growth eastern white pine and eastern hemlock. The area is also valued for hunting, fishing, birdwatching, and uncommon birds such as Canada jays, boreal chickadees, and black-backed woodpeckers.