Later many wagon trains crossed Nevada on the way to California, especially during and after the gold rush of 1849. Travelers going to California over the Old Spanish Trail also crossed S Nevada, and Las Vegas became a station on the route. Guided by Kit Carson, John C. Frémont had explored much of the state between 1843 and 1845, and his reports gave the federal government its first comprehensive information on the area, which the United States acquired from Mexico in the mexican war . These accounts may have aided Brigham Young when he was shepherding the Mormons west to build a new home in the mountains and valleys of Utah.