Now there are fewer than 1,000 mills in the United States, but some are open to the public. If you'd like to visit one, here is a partial list: 1636: Jenney Grist Mill, Plymouth, Massachusetts. mid-1600s: Water Mill, Water Mill, New York. 1682 (rebuilt 1955): Wye Grist Mill, Wye Mills, Maryland. 1689: East Rockaway Grist Mill Museum East ...