In May 1939, she would join Squadron 40-T in protecting American interests during the Spanish Civil War and not return to the US until July 1940, when she carried the royal family of Luxembourg, fleeing from the Nazi occupation of their country.

Trenton was initially built with the capacity to carry 224 mines, but these were removed early in her career to make way for more crew accommodations.

The lower torpedo tube mounts proved to be very wet and were removed, and the openings plated over, before the start of World War II.

[4] On 20 October 1924, while Trenton was conducting gunnery drills off the Virginia Capes near Norfolk, powder bags in her forward turret exploded, killing or injuring every member of the gun crew.

[8] During the ensuing fire, Ensign Henry Clay Drexler and Boatswain's Mate First Class George Cholister attempted to dump powder charges into the immersion tank before they detonated but failed.

Ensign Drexler was killed when the charge exploded, and Boatswain's Mate Cholister was overcome by fire and fumes before he could reach his objective.

[4] Later that month, Trenton steamed north to join in the futile search for lost American motor yacht Leif Ericsson, which went missing with three aboard while en route from Bergen, Norway, to the United States.

The search was suspended on 12 November as further attempts to locate it were deemed "futile" in light of the heavy weather in the region during the two months since the vessel was last heard from.

[9] Following that mission, the light cruiser operated along the United States East Coast until 3 February 1925, when she departed Philadelphia to join the rest of the Scouting Fleet off Guantánamo Bay, Cuba.

On 15 April, the US Fleet put to sea for the Central Pacific and conducted another battle problem en route — this one designed to test fully the defenses of the Hawaiian Islands.

[4] Trenton — in Cruiser Division 2 (CruDiv 2) — sortied with the Battle Fleet on 1 July, for a cruise to the South Pacific and visits to Australia and New Zealand.

Late in August, CruDiv 2 turned homeward and steamed via the Marquesas and Galapagos Islands and the Panama Canal to rejoin the Scouting Fleet near Guantanamo Bay on 4 October.

[4] In January 1926, Trenton joined the other units of the Scouting Fleet and returned to Guantanamo for gunnery drills and tactical exercises.

In mid-March, the units of the Scouting Fleet returned to their home yards for repairs before leaving for summer training cruises with naval reservists and tactical exercises in the area around Narragansett Bay.

Following a review by President Coolidge in June, the various units of the two fleets departed Hampton Roads for their normal summer routines.

[4] In January 1928, Trenton and her division embarked Marines at Charleston and returned to Nicaragua, where they landed to assist in supervising the elections which resulted from Colonel Stimson's visit.

The four light cruisers rendezvoused with the Battle Fleet off the California coast and headed for Hawaii, conducting drills en route.

[4] By late March 1929, Trenton was stationed at Zhifu to prevent a possible outbreak of anti-foreigner pogroms due to the Warlord Rebellion in northeastern Shandong.

For the next four years, Trenton resumed the Scouting Fleet schedule of winter maneuvers in the Caribbean followed by summer exercises off the New England coast.

In January 1936, she retransited the canal and, after an overhaul at the Mare Island Navy Yard, rejoined the Battle Force until late in the spring of 1939.

Trenton patrolled the western Mediterranean and waters off the coast of the Iberian peninsula until mid-July 1940, when she returned to the United States.

[4] During one of these sweeps, on 29 August 1943, while patrolling some 150 nm southeast of Tonga, Trenton received a radar contact which lasted for 15 minutes, but the American commander disregarded it as a regular merchant vessel.

She reached San Francisco on 1 August, and the end of the war found her at Mare Island Navy Yard awaiting inactivation overhaul.