Thompson Pond in Pine Plains, New York is a 75-acre (30 ha) 15,000-year-old glacial kettle pond at the foot of 1,403-foot (428 m) Stissing Mountain. It is the source of Wappinger Creek, a tributary of the Hudson River that drains much of Dutchess County. The pond and mountain are part of a 507-acre (205 ha) nature preserve managed by The Nature Conservancy. The pond was designated a National Natural Landmark in May 1973 for its calcareous bog, unlike the more common acidic bogs in the Northeast.