The event that led to the U.S. acquiring the Philippines, Guam, and Puerto Rico was the Spanish-American War, fought in 1898.

This brief conflict arose from U.S. support for Cuban independence from Spain and was marked by decisive naval victories and land battles. Following the war, the Treaty of Paris was signed, resulting in Spain ceding its territories to the United States. This acquisition marked a significant expansion of U.S. influence in the Caribbean and the Pacific, fueling debates about imperialism and America's role on the world stage.