Peninsula State Park protects Wisconsin's largest contiguous tract of the Niagara Escarpment, a limestone ridge formed by deposits of ocean animals, plants, and mud on the floor of an ancient sea. Rare plants flourish in the ridge's micro-habitats, and trees such as northern white cedar are uniquely adapted to survive on the ledge, with some cedars living for more than 500 years. Along Green Bay, the steep cliffs create a vertical series of natural communities, and the Peninsula Park White Cedar Forest State Natural Area contains five distinct community types that change sharply from the shoreline to the top of the ridge. Two State Natural Areas in the park preserve bench maple and cedar forests much as they were before settlement, and the park's 3,776 acres are designated as a Wisconsin Migratory Bird Stopover Site to protect habitat for migratory birds, including abundant warblers during migration. The headland between Fish Creek and Ephraim became Peninsula State Park in 1909 as Wisconsin's second state park, and tourists came to camp and enjoy nature, with some staying all summer.