 The legislation establishing the National Historic Landmark program does not prevent these from being designated, but in practice these are not often named NHLs "per se", due to administrative costs of their nomination and to the low preservation value of designating them.For the first 16 years of the National Historic Landmarks program, the National Park Service did not consider any sites already within the National Park system for NHL designation, and in fact if a NHL-designated site came into the NPS system it was de-designated.In New York State, the William Floyd House within the Fire Island National Seashore and Ellis Island within the Statue of Liberty National Monument were both deemed NHL-eligible by the Advisory Board but were not designated.