Here she readied to join the escort of the convoy carrying the first troops of the American Expeditionary Force to France, which cleared New York on 14 June, made St. Nazaire, France, after a safe passage through submarine waters on 28 June, and returned to New York on 19 July. After training naval volunteers and reserves for two weeks at Newport, "Charleston" cleared on 16 August for Havana, Cuba, where she supervised the sailing in tow of several former German ships to New Orleans. She next escorted a convoy from Cristobal to Bermuda, where she rendezvoused with a group of British transports, guarding their passage to Hampton Roads.