The Maine spent her active career operating along the East Coast of the United States and the Caribbean. In January 1898, the Maine was sent from Key West, Florida, to Havana, Cuba, to protect U.S. interests during a time of local insurrection and civil disturbances. Three weeks later, on 15 February at 9:40 p.m., an explosion on board the Maine occurred in the Havana Harbor. Later investigations revealed that more than 5 long tons (5.1 t) of powder charges for the vessel's 6 and 10 in (150 and 250 mm) guns had detonated, virtually obliterating the forward third of the ship. The remaining wreckage rapidly settled to the bottom of the harbor. Most of the Maine’s crew were sleeping or resting in the enlisted quarters in the forward part of the ship when the explosion occurred. Two hundred and sixty-six men lost their lives as a result of the explosion or shortly thereafter, and eight more died later from injuries. Captain Charles Sigsbee and most of the officers survived because their quarters were in the aft portion of the ship. Altogether, there were only 89 survivors, 18 of whom were officers. On 28 March, the US Naval Court of Inquiry in Key West declared that a naval mine caused the explosion.
The explosion was a precipitating cause of the Spanish-American War that began in April 1898 and which used the rallying cry, "Remember the Maine!, To hell with Spain!" The episode focused national attention on the crisis in Cuba but was not cited by the William McKinley administration as a casus belli, though it was cited by some who were already inclined to go to war with Spain over their perceived atrocities and loss of control in Cuba.