For a few months in 1898, the United States was at war with Spain. This essentially marked the end of the Spanish Empire and the beginning of the U.S. as a world power. As a result of this brief war, Theodore Roosevelt became president, Cuba became an independent country, Puerto Rico and Guam became American territories, and the U.S. occupied the Philippines for 48 years. That occupation led to the much longer Philippine-American War (1899-1902).