USS Maine (ACR-1) was the United States Navy's second commissioned pre-dreadnought battleship, although she was originally classified as an armored cruiser. She is best known for her catastrophic loss in Havana harbor. Maine had been sent to Havana, Cuba to protect U.S. interests during the Cuban revolt against Spain. On the evening of 15 February 1898, she suddenly exploded, and swiftly sank, killing nearly three quarters of her crew. Though then, as now, the cause and responsibility for her sinking were unclear, popular opinion in the U.S. blamed Spain, and the sinking (popularized in the phrase Remember the Maine, to Hell with Spain!) was one of the precipitating events of the Spanish–American War. Her sinking remains the subject of speculation, with various authors proposing that she sank due to the results of an undetected fire in one of her coal bunkers, that she was the victim of a naval mine, and that she was deliberately sunk for the purposes of driving the U.S. into a war with Spain.
Maine spent her active career operating along the East Coast of the United States and the Caribbean. In January 1898, 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, at 21:40 on 15 February, an explosion on board 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 six and ten-inch guns had detonated, obliterating the forward third of the ship. The remaining wreckage rapidly settled to the bottom of the harbor. Most of Maine's crew were sleeping or resting in the enlisted quarters in the forward part of the ship when the explosion occurred. 266 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 21 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. Advocates of the war 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.