[3] Her Spanish crew unaware that the Spanish–American War had broken out, Callao was steaming toward port in Manila Bay on 12 May 1898 when she was taken completely by surprise by the presence and hostile actions of the U.S. Navy's Asiatic Squadron under Commodore George Dewey and was captured by the protected cruiser Raleigh.

She took part in the 13 August 1898 attack on Manila, serving on the left flank of Army forces, who credited her for very effective gunfire support to the troops ashore.

Along with her participation in the exercises, maneuvers, and visits of the Asiatic Fleet, she gave essential protection to American citizens and interests, often threatened by political disturbance in volatile China.

Callao was decommissioned at Hong Kong on 31 January 1916, and then sailed for Olongapo, Luzon, the Philippines, where she laid up.

This article incorporates text from the public domain Dictionary of American Naval Fighting Ships.