of working lighthouses on Cape Cod and the Islands. Many of Cape Cod's earliest lighthouses featured a light tower that was attached directly to – and centered on the roof of – the keeper's dwelling. A stairway to the lantern room was accessible only from the top floor of the house. This came to be known as a Cape Cod style lighthouse, yet today, the only fully intact specimens are on the west coast of the United States. Most of Cape Cod's lighthouses are operated by the U.S. Coast Guard, with some exceptions, such as the Nauset Light, which has been owned since 1997 by the Cape Cod National Seashore (National Park Service) and operated since 2004 in partnership between that agency and the non-profit Nauset Light Preservation Society. In 1996, both Highland Light and Nauset Light were moved further from the shore because they were each at risk of being lost due to erosion by the sea. Highland Light, then from the ocean, was moved to the west, and Nauset Light, from the bluff, was moved west. The lighthouses of Cape Cod include: Upper Cape: Nobska Light, Wing's Neck Light (privately owned), and Cleveland Ledge Light (also private). Mid Cape: Sandy Neck Light, Hyannis Harbor Light, Lewis Bay Light (or Hyannis Inner Harbor Light, also private), Bishop and Clerks Light, West Dennis Light (formerly the Bass River Light) Lower Cape: Chatham Light, Monomoy Point Light, Stage Harbor Light Outer Cape: Long Point Light, Wood End Light, Race Point Light, Highland Light, Nauset Light, Three Sisters of Nauset, Mayo Beach Light, Billingsgate Island Light Transportation Road Cape Cod is connected to the mainland by a pair of canal-spanning highway bridges, the Bourne and Sagamore that were constructed in the 1930s (replacing a 1912 drawbridge). The two parallel road bridges are four miles apart, with the Bourne Bridge to the west, and the Sagamore to the east. The bridges form a bottleneck, resulting in traffic backups of several miles during the tourist season - especially going on-cape at the beginning of the weekend and off-cape at the end of the weekend. The entire Cape is roughly bisected lengthwise by U.S. Route 6, locally known as the Mid-Cape Highway and officially as the Grand Army of the Republic Highway. Air and water Commercial air service to Cape Cod operates out of Cape Cod Gateway Airport and Provincetown Municipal Airport. General aviation airports