As the Spanish–American War was about to commence in early 1898, McCulloch was on her shakedown cruise, a voyage from Philadelphia via the Suez Canal and the Far East to her first duty station at San Francisco, California.

McCulloch's chief engineer, Frank B. Randall, died of overexertion and heat exhaustion while trying to extinguish the soot fire in the funnel.

[4] As the rock fell astern, Dewey reduced speed to four knots (7.4 km/h; 4.6 mph) so as to reach the head of Manila Bay in time to join action with the Spanish Navy squadron off Cavite at daybreak on 1 May 1898.

In the ensuing Battle of Manila Bay, Dewey′ ships made five firing runs at close range, wreaking devastation on the Spanish squadron.

under fire, guarded the store ships and made ready a 9-inch (23 cm) hawser with which to assist any U.S. ship that ran aground, although that turned out to be unnecessary; at one point, in between firing passes by the U.S. squadron, she intercepted the British mail steamer Esmeralda to convey to the British steamer Dewey's orders for Esmeralda's movements in the vicinity of the battle.

[6] In a 12 June 1898[2] message to United States Secretary of the Navy John D. Long, Dewey commended Captain Hogsdon for the efficiency and readiness of McCulloch during the Battle of Manila Bay.

[7] These four guns, each of which has five revolving 37 mm (1.5 in) barrels, are displayed in pairs to either side of the front of Hamilton Hall facing the parade ground at the United States Coast Guard Academy in New London, Connecticut.

[8] McCulloch arrived at San Francisco, California, on 10 January 1899 and operated on patrol out of that port along the United States West Coast, cruising from the Mexican border to Cape Blanco, Oregon, on law enforcement and lifesaving duties.

Upon her return to San Francisco in 1912, McCulloch resumed patrol operations in her regular cruising district along the U.S. West Coast, with occasional deployments to Alaska.

In 1914, she underwent an overhaul at Mare Island Navy Yard in Vallejo, California, in which her boilers were replaced, fuel tanks were installed, her mainmast was removed, and her bowsprit was shortened.

[1][2] On 24 November 1914, she came to the aid of the steam passenger schooner Hanalei, which had run aground on Duxbury Reef in the Pacific Ocean off California with the loss of 18 lives.

In March 1917, McCulloch underwent another overhaul at Mare Island in which her hull was recaulked and 800 pounds (360 kg) of copper sheathing were removed.

[4] In October 2016, when the U.S. Coast Guard and the U.S. National Oceanic and Atmospheric Administration (NOAA) conducted a routine hydrographic survey as a joint remotely operated vehicle (ROV) training expedition off Point Conception, surveyors noted a congregation of fish – which can indicate the presence of a wreck – three nautical miles off Point Conception at a depth of 300 feet (91 m).

During seven dives by a NOAA VideoRay Mission Specialist ROV operating from the Channel Islands National Marine Sanctuary′s research vessel RV Shearwater (ROV video of the wreck obtained by RV Shearwater https://www.youtube.com/watch?v=s4IlTZYu3jU&t=297s), researchers found a wreck at the site and took images that identified it as that of McCulloch.