Great Captain Island Lighthouse is a lighthouse on Great Captain Island in the western Long Island Sound off the coast of Greenwich, Connecticut, United States. Built in 1829, the first lighthouse, made of stone, was of such poor construction that the walls were severely cracked a decade later. In 1868, a new granite dwelling with attached lantern was completed. The lighthouse is of the same design as lighthouses at Sheffield Island in Norwalk; Morgan Point in Noank; Old Field Point Light and Plum Island in New York; and Block Island North in Rhode Island. In 1890, a fog whistle was added, in 1905 a siren was installed. The lighthouse was deactivated in 1970 when a skeletal tower replaced it. The Town of Greenwich acquired the property in 1973 and had full-time caretakers on the site until the lighthouse became too dilapidated in 2003. A successful restoration effort was completed in 2009 and a non-navigational light was activated in 2012. In 2010, a memorial plaque was installed to "honor the 23 people who lived in Greenwich, or had a connection to the town", who died in the September 11, 2001 attacks.