What was the result of the war?

The result of the Spanish-American War was a swift and decisive American victory that ended Spain's American empire, made the United States a global power with overseas territories, transformed American foreign policy from continental to imperial, and launched debates about empire that have continued for more than a century. The Treaty of Paris signed December 10, 1898 transferred Puerto Rico, Guam, and the Philippines from Spain to the United States and granted Cuba nominal independence under American protectorate. The United States separately annexed Hawaii by joint resolution on July 7, 1898 during the war. American Samoa was acquired in 1899 through partition with Germany. Wake Island was claimed in 1899. By the end of 1899 the United States had acquired its first significant overseas empire.

The status transformation was profound. Before 1898 the United States was a continental power that had expanded by purchase and war within North America while avoiding overseas colonies. Theodore Roosevelt's Secretary of State John Hay called the war a splendid little war and the United States now joined Britain, France, Germany, Russia, and Japan as a colonial power. The military was reorganized for global operations.

The Philippine-American War from February 4, 1899 to July 4, 1902 followed the formal Spanish-American War as Filipino nationalists who had fought Spain now resisted American annexation. About 4,200 Americans died in the Philippine campaign. Estimates of Filipino combatant deaths range from 16,000 to 20,000, with civilian deaths from war-related famine and disease perhaps as high as 200,000 to 250,000.

Domestic political consequences included the formation of the Anti-Imperialist League in 1898, with members including Mark Twain, Andrew Carnegie, William James, and Samuel Gompers. The League opposed annexation of the Philippines on grounds that empire violated republican principles. The Insular Cases, a series of Supreme Court rulings from 1901 onward, held that the Constitution did not fully apply to inhabitants of unincorporated territories. The legal category of unincorporated territory was created to allow American sovereignty without full constitutional citizenship.

Theodore Roosevelt rose to political prominence through his Rough Riders charge on Kettle Hill on July 1, 1898 and became governor of New York in 1899, vice president in 1901, and president on September 14, 1901 after William McKinley's assassination. Roosevelt's Big Stick foreign policy, the Roosevelt Corollary to the Monroe Doctrine of December 6, 1904, and the Panama Canal building from 1904 to 1914 reflected the imperial confidence the war produced. The war also accelerated naval expansion. The Great White Fleet, sent around the world from 1907 to 1909, demonstrated American naval reach. The United States entered World War I in 1917 and World War II in 1941 as a global power, a status the Spanish-American War initiated.