The Mentor Marsh Nature Preserve has been in the care of the state and the Cleveland Museum of Natural History (CMNH) since 1966. At 850 acres, Mentor Marsh is the largest coastal wetland in northeast Ohio and over 650 acres is managed as a State Nature Preserve. The Preserve's nature center is operated by CMNH and a local Board of Managers. It is open the first Sunday of every month from 11am to 4pm from November to March. From April to October, it is open on every Saturday and Sunday from noon to 5 p.m. Naturalists lead walks through the preserve at 2 p.m. every Sunday the nature center is open. Field trips and class lessons on the Mentor Marsh can be arranged by appointment. Volunteers are welcome! No dogs or bikes are permitted in the State Nature Preserve.