Traité naval de Londres
On 11 November, "St. Louis" arrived at Philadelphia where, on completion of pre-inactivation overhaul, she was decommissioned on 3 March 1922. In reserve until struck from the Navy List on 20 March 1930, "St. Louis"'s hulk was sold for scrap on 13 August in accordance with the provisions of the London Naval Treaty and Second London Naval Treaty for the limitation and reduction of naval armament.