Mantle Rock Nature Preserve was protected for its rare and fragile sandstone glades, low-fertility habitats that support a unique plant community including the state's only known occurrence of June grass, along with prickly pear cactus, rushfoil, hairy lipfern, little bluestem, pinweed, and poverty grass. Its centerpiece is a 30-foot-high natural sandstone arch spanning 188 feet, the longest natural arch east of the Mississippi River, formed about 320 million years ago during the Pennsylvanian Period of the Paleozoic Era, and the preserve also includes bluffs, rock shelters, honeycomb formations, fluorite deposits, and a rock-lined stream. The Reynolds Metal Company donated 190 acres in 1988 to establish the preserve, which expanded in 1995 with the 175-acre Calendar Tract and the two-acre Mandy Falls tract, while nearly 1,900 additional nearby acres were also protected and became the Livingston County Wildlife Management Area and State Natural Area, preserving white oak forest and rare and threatened species such as Price's potato bean. Within this fire-adapted landscape, ecological evidence indicates that Native Americans used fire to manage the surrounding area, and prescribed burning and manual invasive-species removal are now used to maintain glade, prairie, and woodland communities, support grasses and wildflowers, and improve pollinator habitat.