9.4Becoming a world power

The United States entered the century as a rising power with a new overseas empire won from Spain, including the Philippines and Puerto Rico. Roosevelt projected American might, building a modern navy and securing the Panama Canal (completed 1914), which linked the oceans and confirmed U.S. dominance in the hemisphere.

For decades Americans had heeded Washington's warning against foreign entanglements. But growing economic and naval power made isolation harder to maintain. The nation increasingly intervened in Latin America and looked outward across the Pacific. When world war engulfed Europe, the United States would find neutrality impossible to sustain—and would emerge transformed.