On 2 November 1917, "Massachusetts" and "Bunker Hill" were purchased by the US Navy for $1,350,000 each and sent to the Boston Navy Yard for conversion to minelayers. Sister ship Old Colony was prchased for $1,150,000. Before "Massachusetts" completed her conversion she was renamed "Shawmut" after the Shawmut Peninsula on the Charles River that flows through Boston. She was the second ship in the Navy to carry the name and was commissioned as USS "Massachusetts" (ID 1255) on 7 December 1917, with Captain Wat T. Cluverius in command.