The sinking of the USS Maine in Havana harbor on February 15, 1898, was the catalyst that led to the Spanish-American War.
The United States had been suspicious of Spain's rule over Cuba for some time, and the sinking of the Maine, in which 266 American sailors died, was seen as an act of war by the United States.
Although the exact cause of the explosion that sank the Maine has never been conclusively determined, the United States government quickly blamed Spain and used the sinking as a justification for declaring war on Spain on April 25, 1898.
The Spanish-American War lasted for less than four months and resulted in the United States gaining control of Cuba, Puerto Rico, Guam, and the Philippines from Spain.