What war did the U.S. fight in 1898 to acquire territories such as Puerto Rico and the Philippines?

The war fought by the U.S. in 1898 to acquire territories such as Puerto Rico and the Philippines is the Spanish-American War. This conflict emerged from the desire of the United States to assist Cuba in its struggle for independence from Spain, leading to heightened tensions that resulted in war. The Treaty of Paris, which concluded the war, resulted in Spain ceding Puerto Rico, Guam, and the Philippines to the U.S. The war marked a significant turning point in U.S. foreign policy, transitioning the nation into an imperial power with overseas territories.

In contrast, the Mexican-American War occurred in the mid-19th century, focusing on territorial expansion primarily in what is now the southwestern United States. The Civil War was a domestic conflict primarily over issues of slavery and state's rights, while World War I occurred much later, in the early 20th century, and involved the U.S. in a global conflict rather than the acquisition of territories from another imperial power.