Brigham Young decided that the Mormons would sit out the Civil War. He saw the conflict as God’s punishment of the United States for its past mistreatment of his church, especially its failure to protect Joseph Smith, the Mormons’ founder who was murdered by an Illinois mob in 1844. By JOHN G. TURNER
There was Lot Smith and his 100-man federal cavalry company raised in Utah during the spring of 1862. Their role was to protect the trail and telegraph line in present-day southwestern Wyoming between Fort Bridger and Fort Laramie until other regiments could arrive.
But their service lasted only 90 days. An effort to re-enlist them, and even to recruit more extensively in the territory, was discouraged by the territorial governor, Stephen S. Harding, a Lincoln appointee.
Although there was the Mormon Battalion- http://www.lds.org/locations/san-diego-mormon-battalion-historic-site
The men of the Mormon Battalion are honored for their willingness to fight for the United States as loyal American citizens. Their march of 2,000 miles from Council Bluffs, Iowa to California is one of the longest military marches in history. They participated in the early development of California by building Fort Moore in Los Angeles, and the courthouse in San Diego.