“Mexican-American War,” Church History Topics
Between 1846 and 1848—precisely when Latter-day Saint pioneers began to migrate to the valley of the Great Salt Lake—the United States of America and Mexico fought a war that altered the social and political landscape of the North American West. Not only did the Saints experience the effects of this war in their efforts to relocate and to build settlements, but some also participated in the conflict as soldiers in the Mormon Battalion.
The war began over a dispute between the two countries regarding the Republic of Texas, a large territory in the middle of the continent that had been contested by Spaniards, Mexicans, white settlers from the United States, and Comanches. When the United States Congress offered statehood to the Republic of Texas and it accepted, Mexico denounced the annexation. A border dispute around the Rio Grande escalated into armed hostilities, and in 1846 Congress declared war on Mexico.
At this time, the Latter-day Saints, who had recently been forced to leave their homes in Illinois, were feeling betrayed by the United States government and many of the American people. Early in 1846, most Latter-day Saints had left their homes in and around Illinois with the intent to settle in the region of the Great Salt Lake, which was then part of Mexico. Following the declaration of war, a Latter-day Saint leader persuaded President James K. Polk to raise a battalion of Latter-day Saint soldiers for the war. The soldiers’ pay would help fund the Saints’ migration west. Brigham Young urged members of the battalion not to have “contentious conversations” with the people of Mexico, to “treat prisoners with the greatest civility,” and not to take a life if at all possible.1 In the end, the battalion never engaged in combat in the war.
The U.S. Army invaded Mexico in early 1847 and captured Mexico City within the year. In 1848 the two countries agreed to the Treaty of Guadalupe Hidalgo, which ended the war and transferred a vast amount of territory to the United States, including the region where the Latter-day Saints had chosen to settle. A portion of the area ceded to the United States became Utah Territory in 1850. Latter-day Saints who had fled the United States for the West came once again under the political authority of the U.S. government, and some of the difficulties they had encountered during the previous decade returned. Tensions mounted between federally appointed territorial officials and the Latter-day Saints over the administration of local government and over religious freedom.2
Immigration sparked by the annexation of western territories and by the California Gold Rush brought increased traffic and commerce to Latter-day Saint communities.3 The changing social and political landscape after the war opened up new opportunities for the Saints as they attempted to build lasting enterprises and permanent cities in what would become the states of Utah, Nevada, Arizona, and California.4