Placed in commission in reserve on 14 September 1912, "Charleston" joined the Pacific Reserve Fleet, remaining at Puget Sound as a receiving ship through early 1916, aside from a voyage to San Francisco in October 1913 as flagship for the Commander-in-Chief, Pacific Reserve Fleet. From 1912 through early 1916, she was receiving ship at the yard. With a new assignment as tender for the submarines based in the Panama Canal Zone, "Charleston" arrived at Cristobal, C.Z. on 7 May 1916, for a year of operations with submarines, reconnaissance of anchorages, and gunnery exercises.