10 September 1918 by Bethlehem Shipbuilding at their yard in Quincy, Massachusetts, with the yard number 332. Named for Roderick S. McCook, the ship was launched on 31 January 1919, sponsored by Mrs. Henry C. Dinger. McCook was commissioned on 30 April 1919. Following a period performing shakedown training, McCook was assigned to Destroyer Force, Atlantic Fleet. She operated along the east coast of the United States until decommissioning at Philadelphia on 30 June 1922. McCook remained in the Atlantic Reserve Fleet until recommissioned on 18 December 1939. The next year McCook was designated for exchange under the Destroyers for Bases Agreement with the United Kingdom. Transfer to the UK By 1940, the United Kingdom and the Commonwealth nations were fighting the Axis powers alone after the fall of France. The convoy route between North America and the United Kingdom was under attack by German U-boats and required protection, but the British lacked adequate ships to defend the shipping lanes. That year, the US offered 50 "flush deck destroyers" to the UK in exchange for leases to British bases around the world. In September, the deal was sealed and 50 vessels of the Clemson and Wickes classes were transferred to the UK. Renamed the Town class by the British, their new names were chosen from towns with names common to both nations. After entering British service, the destroyers were modified with British radar, asdic and depth charge throwers. Two of the torpedo tube mounts were removed to make space for an Oerlikon 20 mm cannon, the aft 4-inch gun was replaced by a British 12-pounder gun and Type 273 radar was installed. Two boilers were removed and fuel storage was increased to improve range. The destroyer's final layout was three 20 mm Oerlikon cannon, one 3-inch gun, two .50 caliber machine guns, depth charge roller racks, one 21-inch torpedo tube mount sited on the deck centreline and the bridge area was revamped to make room for the new electronic equipment. Steaming to Halifax, Nova Scotia, McCook arrived on 20 September 1940. Decommissioned on 24 September by the United States Navy, the destroyer was transferred to the United Kingdom on the same date, but due to manpower shortages in the Royal Navy, she was retransferred immediately to the Royal Canadian Navy and commissioned as HMCS St. Croix (I81). Following the Canadian practice of naming destroyers after Canadian rivers (but with deference