One cause of the Spanish-American War: the United States wanted an empire. The United States needed coaling stations in the Pacific in order for its ships to reach the rich markets of China. This is one reason why the United States captured Guam and the Philippines during the Spanish-American War. Another cause of the war would be Spain's inability to control Cuba. Cuban rebels started to agitate for their independence. When the Spanish general in charge of the island put the Cubans in concentration camps in order to pursue the insurgents, many Cubans died due to overcrowding. The Cuban insurgents attacked both American sugar interests and Spanish businesses. The United States wanted to protect its own economic interests as well as exert its ability to control the Western hemisphere.
Yellow journalism was another cause of the war. William Randolph Hearst made a great deal of money by selling the narrative that the Spanish were barbaric and the Cubans were good. He even sent noted artist Frederic Remington to the island in order to draw pictures of Spanish atrocities. Remington did not see any, but Hearst continued to push for war by showing the Spanish as barbaric and inept. When the USS Maine sank off the coast of Havana, the American press clamored for war. It was only later proven that the ship sank due to an internal powder magazine explosion and not a Spanish mine.
There were many effects of the war. While the United States gained the Philippines and Guam, it also gained its own insurgent war in the Philippines, as Emilio Aguinaldo led forces against the occupying Americans in order to take back the islands for Filipino rule. This war would kill thousands of Filipinos and drag on for four years—longer than the Spanish conflict. The war would also prove to be politically divisive as some in the United States did not want the nation to become imperialistic. The United States gained the port of Guantanamo and the island of Puerto Rico which it still administers today. The war unified the Southern and Northern members of Congress who still felt separated by the Civil War. The war also opened Cuba to greater exploitation by American commercial interests, much to the consternation of many Cubans who expected their lives to improve after the expulsion of the Spanish.