Lightship "Frying Pan" is listed on both the New York State and Federal Registers of Historic Places, as it is one of 13 lightships remaining from more than 100 built. The US Coast Guard used lightships as floating lighthouses to guard other ships from running aground on shoals, or submerged rocks, that were too far from land to be served by a lighthouse on shore. Many were also used to mark the entrances to harbors. New Yorkers may be familiar with the Lightship Ambrose which marked the entrance of New York Harbor, and is currently docked at the South Street Seaport Museum.