The event that led to the start of the Spanish-American War was the explosion of the USS Maine in Havana Harbor on February 15, 1898. This incident spurred public outrage in the United States and heightened tensions between the U.S. and Spain, which was viewed as potentially responsible for the explosion. The war was fueled by American imperialist sentiment, the desire to liberate Cuba from Spanish rule, and other underlying political and economic interests. Ultimately, the conflict lasted only a few months, resulting in the Treaty of Paris and significant territorial gains for the United States in the Caribbean and the Pacific.