Utah War
After Mormons established a community hundreds of miles away in the Salt Lake Valley in 1847, anti-Mormon activists in the Utah Territory convinced President Buchanan that the Mormons in the territory were rebelling against the United States under the direction of Brigham Young. In response, in 1857 Buchanan sent one-third of United States's standing army to Utah in what is known as the Utah War. During the Utah War, the Mountain Meadows massacre occurred.