Bay Creek Wilderness is a 2,866-acre protected roadless area in southern Illinois within Shawnee National Forest, centered on the upper reaches of Bay Creek, a tributary of the Ohio River. Once used for agriculture, the land became part of the national forest after federal acquisitions in the 1930s, and in 1990 it was designated as one of seven small wilderness parcels under the Illinois Wilderness Act. As a regenerated second-growth forest, it reflects both ecological recovery and wilderness preservation. Bay Creek shapes the landscape, connects hydrologically with nearby Burden Falls Wilderness, and flows toward Bell Smith Springs.