Spanish-American War
The Spanish-American War took place in 1898. It was an American victory.
The last major pieces of the Spanish Empire in the New World were Puerto Rico and Cuba. The Cubans rebelled, leading the Spanish authorities to take repressive measures. The USS Maine was blown up by the Spanish in Havana harbor. War was declared shortly afterward.
Under the slogan, "Remember the Maine", the Americans struck back with naval victories in the Caribbean and near the Philippines. In the Battle of Manila Bay, Commodore George Dewey on the USS Olympia (now moored in Philadelphia), said the famous command, "You may fire when ready, Gridley."
On land, the Rough Riders, dismounted and led by Theodore Roosevelt, charged up San Juan Hill in Cuba, defeating the Spanish.
In the peace settlement Cuba, Puerto Rico, Guam and the Philippines were ceded to the United States.