The SpanishAmerican War (April 21 August 13, 1898) was a period of armed conflict between Spain and the United States. Hostilities began in the aftermath of the internal explosion of USS Maine in Havana Harbor in Cuba, leading to United States intervention in the Cuban War of Independence. The war led to the United States emerging predominant in the Caribbean region, and resulted in U.S. acquisition of Spain's Pacific possessions. It led to United States involvement in the Philippine Revolution and later to the PhilippineAmerican War.

The main issue was Cuban independence. Revolts had been occurring for some years in Cuba against Spanish colonial rule. The United States backed these revolts upon entering the SpanishAmerican War. There had been war scares before, as in the Virginius Affair in 1873. But in the late 1890s, American public opinion swayed in support of the rebellion because of reports of concentration camps set up to control the populace. Yellow journalism exaggerated the atrocities to further increase public fervor and to sell more newspapers and magazines.The business community had just recovered from a deep depression and feared that a war would reverse the gains. Accordingly, most business interests lobbied vigorously against going to war. President William McKinley ignored the exaggerated news reporting and sought a peaceful settlement. However, after the United States Navy armored cruiser Maine mysteriously exploded and sank in Havana Harbor on February 15, 1898, political pressures from the Democratic Party pushed McKinley into a war that he had wished to avoid.

On April 20, 1898, McKinley signed a joint Congressional resolution demanding Spanish withdrawal and authorizing the President to use military force to help Cuba gain independence. In response, Spain severed diplomatic relations with the United States on April 21. On the same day, the United States Navy began a blockade of Cuba. Both sides declared war; neither had allies.

The 10-week war was fought in both the Caribbean and the Pacific. As United States agitators for war well knew, United States naval power would prove decisive, allowing expeditionary forces to disembark in Cuba against a Spanish garrison already facing nationwide Cuban insurgent attacks and further devastated by yellow fever. The invaders obtained the surrender of Santiago de Cuba and Manila despite the good performance of some Spanish infantry units, and fierce fighting for positions such as San Juan Hill. Madrid sued for peace after two Spanish squadrons were sunk in the battles of Santiago de Cuba and Manila Bay, and a third, more modern fleet was recalled home to protect the Spanish coasts.The war ended with the 1898 Treaty of Paris, negotiated on terms favorable to the United States. The treaty ceded ownership of Puerto Rico, Guam, and the Philippine islands from Spain to the United States and granted the United States temporary control of Cuba. The cession of the Philippines involved payment of $20 million ($650 million today) to Spain by the U.S. to cover infrastructure owned by Spain.The defeat and loss of the Spanish Empire's last remnants was a profound shock to Spain's national psyche and provoked a thorough philosophical and artistic reevaluation of Spanish society known as the Generation of '98. The United States meanwhile not only became a major power, but also gained several island possessions spanning the globe, which provoked rancorous debate over the wisdom of expansionism.

William McKinley (January 29, 1843 – September 14, 1901) was the 25th president of the United States, serving from 1897 until his assassination in 1901. He was president during the Spanish–American War of 1898, raised protective tariffs to boost American industry, and rejected the expansionary monetary policy of free silver, keeping the nation on the gold standard.

A Republican, McKinley was the last president to have served in the American Civil War; he was the only one to begin his service as an enlisted man, and end as a brevet major. After the war, he settled in Canton, Ohio, where he practiced law and married Ida Saxton. In 1876, McKinley was elected to Congress, where he became the Republican Party's expert on the protective tariff, which he promised would bring prosperity. His 1890 McKinley Tariff was highly controversial and, together with a Democratic redistricting aimed at gerrymandering him out of office, led to his defeat in the Democratic landslide of 1890. He was elected governor of Ohio in 1891 and 1893, steering a moderate course between capital and labor interests. With the aid of his close adviser Mark Hanna, he secured the Republican nomination for president in 1896 amid a deep economic depression. He defeated his Democratic rival William Jennings Bryan after a front porch campaign in which he advocated "sound money" (the gold standard unless altered by international agreement) and promised that high tariffs would restore prosperity.

Rapid economic growth marked McKinley's presidency. He promoted the 1897 Dingley Tariff to protect manufacturers and factory workers from foreign competition and in 1900 secured the passage of the Gold Standard Act. He hoped to persuade Spain to grant independence to rebellious Cuba without conflict, but when negotiation failed, requested and signed Congress's declaration of war to begin the Spanish-American War of 1898. The United States victory was quick and decisive. As part of the peace settlement, Spain turned over to the United States its main overseas colonies of Puerto Rico, Guam and the Philippines while Cuba was promised independence, but at that time remained under the control of the United States Army. The United States annexed the independent Republic of Hawaii in 1898 and it became a United States territory.

Historians regard McKinley's 1896 victory as a realigning election in which the political stalemate of the post-Civil War era gave way to the Republican-dominated Fourth Party System, beginning with the Progressive Era. McKinley defeated Bryan again in the 1900 presidential election in a campaign focused on imperialism, protectionism, and free silver. His achievements were cut short when he was fatally shot on September 6, 1901, by Leon Czolgosz, a second-generation Polish-American anarchist. McKinley died eight days later and was succeeded by Vice President Theodore Roosevelt. As an innovator of American interventionism and pro-business sentiment, McKinley is generally ranked above average. His popularity was soon overshadowed by Roosevelt's.