She remained in the Atlantic Reserve Fleet until 30 December 1913, when she was sent to Pensacola, Florida for use as a support ship for the creation of the Naval Air Station Pensacola. She took on a group of nine officers and twenty-three enlisted men along with aircraft and other equipment. She arrived there on 20 January 1914, where the men set about establishing the base. In April, "Mississippi" received orders to carry a 500-man detachment from the 2nd Marines, who had by then transferred to Pensacola, to Tampico, Mexico after the Tampico Affair that saw a minor confrontation between Mexican soldiers and USN sailors. She also carried a pair of seaplanes and supporting equipment. The ship got underway for Veracruz, Mexico on 21 April, arriving there four days later. On 26 April, she transferred both seaplanes to shore, along with their ground crews and other equipment. The aircraft operated under command of Patrick N. L. Bellinger in the area for a month and a half during the occupation of Veracruz, conducting reconnaissance and searching the surrounding sea for naval mines, supported by men from "Mississippi". In late May, the ship departed for Pensacola, where she remained until 28 June, thereafter steaming north for Hampton Roads.