SIREN was the seventh of the 20 New York 32–class sloops built by the Nevins yard of City Island, New York, during the winter of 1935–36; she carries sail No. 20. Designed by Olin Stephens, these 45-footers were commissioned by the New York Yacht Club (NYYC) as replacements for the storied New York 30s built by the Herreshoff Manufacturing Co. in 1905. Originally christened FOLLY, she was delivered to Junius Spencer Morgan III—grandson of the American banker J.P. Morgan—an avid racer and previous commodore of both the NYYC and Seawanhaka Yacht Club. All 20 boats built to this design were purchased by members of the NYYC and quickly proved successful in spirited competition on the waters of Long Island Sound.
By the 1960s, FOLLY had changed hands numerous times before being purchased by Franklin D. Roosevelt Jr., son of the former president, a U.S. congressman himself, and recently appointed to the office of under secretary of commerce by fellow sailor John F. Kennedy. Renamed HALF MOON, she spent her time sailing on the Chesapeake Bay and in New England with the Roosevelt family. During the winter of 1976, Roosevelt commissioned Martha’s Vineyard Shipyard to convert her marconi sloop rig—an aluminum replacement already—into a yawl. The island boatyard had previously installed a new diesel auxiliary, replacing an earlier gasoline engine, and partially reframed her midsection; actually, Martha’s Vineyard Shipyard reframed the hull twice in rapid succession after the frames of the first replacement set were damaged while the yacht was on charter as an AMERICA’s Cup spectator.