The ship's AA armament were originally augmented by three quadruple /75 gun mounts by early 1942, however, these didn't prove to be reliable and were replaced by twin Bofors guns along with 14 Oerlikon cannons by the end of the war. It was reported that "Cincinnati" also mounted a pair of Army 40mm Bofors guns. "Cincinnati" began her career with the Scouting Fleet in operations along the eastern seaboard and the Caribbean, until February 1927, when transferred to duty in the Far East, based at Shanghai. This duty only lasted until April 1928, when she sailed for Newport, Rhode Island, and conducted operations along the east coast again, until 1932. "Cincinnati" left for the Pacific joining the Battle Force, with occasional trips to the east coast, until 1939, when she was again reassigned to Atlantic duty. On 12 February 1935, she rescued six members of the crew of the downed airship USS "Macon". "Cincinnati" transferred to Pearl Harbor in April 1940, sailing for Guam and the Philippines and conducting transport duty at the end of the year. After a year in the Pacific "Cincinnati" returned to the Atlantic to join her sister ships in the expanding neutrality patrols in the western Atlantic. After the United States entered the war, she continued patrolling, along with convoy escort duties, blockading the French fleet at Martinique, and searching for German blockade runners. On 21 November 1942, along with her sister and the destroyer , they spotted . The crew had begun to scuttle the ship, but the boarding party that had been dispatched was able to reach the ship and discover her true identity, a German blockade runner. They took the crew of 62 as prisoners, before she sank. "Cincinnati" received an overhaul at New York, in early 1944, before serving as the escort flagship for three convoys crossing from New York to Belfast, Northern Ireland, from March 1944 to July 1944. She sailed for the western Mediterranean on 28 July, to assist with the assault on southern France, before again returning to New York for overhaul. She then joined the 4th Fleet at Recife, Brazil, on 17 November, and finished out the war in the European Theater patrolling the south Atlantic shipping lanes. "Cincinnati" carried out two midshipmen training cruises during the summer of 1945. On 29 September, she arrived at Philadelphia, where a Board of Inspection and Survey recommended that she be taken out of commission. She was decommissioned 1 November 1945, and scrapped on 27 February 1946.