Officially, the Later-day Saints stood with the Union during the Civil war. Abraham Lincoln sent a telegram to Brigham Young to ask him what Utah intended to do. Brigham's reply was that the Saint would stand with the Union and would guard the telegraph lines that led from the rest of the country to California. This freed up the army troops that were in Utah to return to the east to fight in the war. However, beyond this, the Church did not take much of a position on the Civil war. The reason for this is because the Saints in general were not very happy with the country in general at this time. To understand this you need to understand some aspects of LDS History. From the time the Church was first organized to the time that they moved to Utah, its members had been persecuted and driven out by the citizens of several different communities in the United States. All attempts to seek legal protection and just recompense for the indignities that were heap upon them ultimately fell on deaf ears. In 1846 (just 15 years before the beginning of the Civil War) they were driven completely out of what was then the United States. Then in 1857, the Untied States sends an army to Utah to put down a nonexistent rebellion (see question about the Utah War). Add to this the early stages of the legalized persecution the federal government over polygamy and you can see why the Saints were not very happy with the United States at that time. Because of this, the Saints saw the Civil War as being the Devine punishing the U.S. for the way it had treated them. As such Utah did not contribute any troops to the Union army as they had for the Mexican-American War. These hard feelings took a number of generations to dissipate. Because of this Utah did not contribute much in the way of recruits to the military until World War I. However, since that time Utah and the Latter-day Saints have more than done their share to help keep this country free.

Yes. That position (taken in 1838) was that there would be one, that it would start in South Carolina, and that it would be pinned on the issue of slavery. The Church was opposed to slavery (which was a root cause of the troubles in Missouri, a slave state).