In U.S. state park systems, recreation areas may also fail to meet some criteria to be designated state parks, such as having multiple non-contiguous properties. Size is not necessarily a defining criterion. For instance, in Michigan, the largest state recreation area, Waterloo Recreation Area is 20,500-acre (83 km2) while the smallest state park is the 31-acre (0.13 km2) Tri-Centennial State Park and Harbor.