On 25 April 1898, U.S. Congress declared war on Spain, formalizing the tensions that had existed between the two countries over Cuba into what would become known as the Spanish-American War.
Although Cuba had been a Spanish possession for hundreds of years, American interest in the colony grew in the 19th century, due in part to the Monroe Doctrine (1823), which made it clear that the United States wouldn’t let European powers further colonize the Americas. The American interest in Cuba intensified when, in the later part of the century, Cubans began to seriously fight against Spain for their independence.
In 1897, Spanish leaders attempted to put down a Cuban revolt through the brutal use of concentration camps. American newspaper magnates William Hurst and Joseph Pulitzer capitalized on the uprising, exaggerating the Spanish atrocities in order to sell more papers and whipping the American population into an indignant fury. At the same time, American businesses with interests in Cuba, afraid that the fight for independence would hurt them economically, pressured the government to intervene. President McKinley favored solving the problem diplomatically, and in late 1897 an agreement was reached with Spain for Cuban independence to begin in January 1898.
An uprising in Havana in January caused McKinley to send the USS Maine to Cuba as a precautionary measure. But on 15 February, after an explosion, the Maine sank and 266 sailors died. Despite the public outcry, McKinley was able to postpone war with Spain—until 28 March, when an investigation into the explosion pointed to the Spanish.
By mid-April, McKinley felt increasingly pressured by Congress and the public to go to war with Spain. On 19 April, the president signed a resolution demanding that Spain withdraw from Cuba and allowing America to use force to ensure that it happened. The resolution outraged Spain, and they recalled their diplomatic representation in the United States. Shortly thereafter, on 23 April, Spain declared war, and America followed suit two days later on the 25th.