When the Saints arrived in the Salt Lake Valley, Utah was claimed by Mexico. Any hopes the Saints had of permanently escaping the United States were dashed in 1848, however, after the U.S. victoriously concluded the Mexican War and signed the Treaty of Guadalupe Hidalgo, forcing Mexico to renounce any claim to Texas north of the Rio Grande, and to cede California, Nevada, Utah, western Colorado, Arizona, and New Mexico. In 1849, Brigham Young was elected territorial governor, and the Saints made an application for statehood. The name they proposed for their state was "Deseret," a Book of Mormon word meaning "honey bee." (The beehive is still used as a symbol for the state of Utah.) The territory proposed for the state was vast, and included all of modern Utah and Nevada, most of Arizona, parts of Oregon, Idaho, Wyoming, Colorado, New Mexico, and southern California. The proposed super-state would have shared a more than 400-mile-long border with Mexico, and would have included a Pacific coastline from present-day southern Los Angeles to San Diego.

The 1849 application and five subsequent applications for statehood between 1856 and 1887 were, however, denied. The national government refused to consider them as long as it was convinced that the Utah would be governed not by democratic principles, but by the Mormon theocracy.