 = Greens Ledge Light = 
 
 Greens Ledge Lighthouse is a sparkplug lighthouse in Connecticut , United States , off the southwest end of the Norwalk Islands , Long Island Sound , near Norwalk , Connecticut . It is on north side of the west end of Greens Ledge , west of Norwalk Harbor a mile south of the entrance to Five Mile River at Rowayton , and just over a mile southwest of Sheffield Lighthouse . Completed in 1902 , it was constructed by the Philadelphia Construction Company . The light is 52 feet ( 16 m ) tall and is made of five courses that make up its four stories . The lantern measures 7 feet ( 2 @.@ 1 m ) in diameter . The Greens Ledge Light replaced the Sheffield Island Light . Originally , the light had a fifth @-@ order Fresnel lens , but a fourth @-@ order Fresnel lens was installed in May 1902 , just three months into its operation . Currently a VRB @-@ 25 is in use and it has alternating white and red flash every 24 seconds . The light was added to the National Register of Historic Places as Greens Ledge Lighthouse on May 29 , 1990 . 
 
 = = Design = = 
 
 In the 1890s , the lighthouse was first formally proposed to mark the Norwalk Harbor . In 1899 , the United States Congress appropriated $ 60 @,@ 000 for the establishment of a light and fog signal at Greens Ledge . In 1900 , the Philadelphia Construction Company was contracted to construct the foundation and the superstructure . The design for this type of lighthouse was first realized in 1873 , from Major Eliiot of the Lighthouse Board . The foundation form is made of identical curved @-@ iron plates with top inward @-@ pointing flanges that are bolted together and secured with knees . The assembled rings are lowered into the water and filled with concrete or stone , concrete for the Greens Ledge Light . A series of photographs from the work in 1901 shows the assembly of the three lower courses at Wilson 's Point , the lowering of the cylinder and the light in the fall of 1901 prior to a deposit of protective riprap . 
 The 52 @-@ foot ( 16 m ) tall Greens Ledge Light was completed in 1902 and serves as a typical example of a sparkplug lighthouse . Located in 10 feet ( 3 @.@ 0 m ) of water , the foundation flares out to support the deck the lighthouse is built on and includes a cavity for the lighthouse 's brick basement and cisterns . The four @-@ story structure of the lighthouse is assembled from five courses of curved iron plates . The interior is lined with brick to insulate and strengthen the tower and to " provid [ e ] an anchorage for the winding cast @-@ iron stairs which rise on the periphery of each story , " writes historian Dorothy Templeton . 
 The plain prefabricated features underwent a period of development of which the Greens Ledge Light was part of a second phase . Templeton describes , " the brackets which support the watchroom gallery and covered deck [ as having ] a simplified classical detailing and [ the ] rectilinear window sashes are enclosed in shallower , plainer cast @-@ iron surrounds . " A deck encircles the light on above the first story , the watchroom and lantern . The original roofing and some cast @-@ iron stanchions of the decks are able to be seen atop the riprap . The cast @-@ iron door to the lighthouse faces south and at the time of nomination the windows were sealed with plywood . The first floor of the lighthouse serves as the kitchen . The second level has two rooms split by a partition with the smaller room being a bathroom . The third level was not divided , but did not have a description in the National Historic Register of Places survey . The fourth floor has six porthole windows and has had much of its woodwork removed and part of the cast @-@ iron floor and brick wall are exposed . The lighthouse 's lantern measures 7 feet ( 2 @.@ 1 m ) in diameter . Once active , the Sheffield Island Light was discontinued . 
 
 = = Service = = 
 
 Originally , the light had a fifth @-@ order Fresnel lens , but a fourth @-@ order Fresnel lens was installed in May 1902 , just three months into its operation . The light characteristic was a fixed white light with a red flash every 15 seconds . In 1972 , the light was automated and the Fresnel lens was replaced with a modern optic . The light continues to serve as an active aid to navigation . In 1987 , a FA @-@ 251 was installed before the current lens , a VRB @-@ 25 was installed . The current light characteristic is an alternating white and red flash every 24 seconds . The white and red flashes can be seen for 18 nautical miles and 15 nautical miles , respectably . 
 During its service , the tower began to tilt and the keepers moved all the furniture to one side of the tower . The problem was reported to have been exacerbated following the 1938 New England hurricane . 
 
 = = Importance = = 
 
 The light was added to the National Register of Historic Places as Greens Ledge Lighthouse on May 29 , 1990 . It is listed as " significant as a typical example of a pre @-@ fabricated cast @-@ iron conical lighttower on a cast @-@ iron tubular foundation . " 
 The lighthouse served as a source of inspiration for Walter DuBois Richards , an artist , for over forty years . Since 1935 , swimmers have been competing annually in the Arthur J. Ladrigan Swim Race , a one @-@ mile ( 1 @.@ 6 km ) race from the lighthouse to Bayley Beach in the Rowayton section of Norwalk . 
 
 = = List of keepers = = 
 
 This list includes known keepers , but excludes assistants and non @-@ officers of the Coast Guard . 
 
 