In 1854 the U.S. attempted to buy Cuba from Spain. Spain stated that they'd rather seen Cuba sink into the ocean.
Jose Marti was a poet and a journalist in New York that started a revolution. He purposely destroyed U.S. property in Cuba so the U.S. could help him free Cuba.
America and Spain weren't on good terms, so the U.S. sent the USS Maine to protect their property and citizens. The ship blew up on February 15, 1898, but due to yellow journalism, U.S. newspapers said Spain was the cause of the explosion and 266 deaths.
After the explosion, the U.S. declared war with Spain and it lasted six months. The Rough Riders won a very small battle in the war and Teddy Roosevelt was their leader.
At the end of the war, the U.S. and Spain signed a cease-fire on August 12, 1898. Meeting up in Paris they agreed on a treaty, which gave the islands of Guam and Puerto Rico, and sold the Philippines to the U.S.
The Treaty of Paris argued whether or not the U.S. had the right to annex the Philippines. On February 6, 1899 the annexation question was settled with the senates approval of the treaty of Paris.