Hours: Grounds and historic buildings open Wed.-Sun. 10-5, early June-Aug. 31; Sun. 10-5, Sept. 1 to mid-Oct. Grounds only Fri.-Sun. 9-5, mid-Apr. to early June; Fri.-Sat. 9-4, Sept. 1 to mid-Oct. Farmers market Sun. 10-2, late May to mid-Oct. Closed Memorial Day, July 4, Labor Day and Michigan International Speedway race Sundays.