Latter-day Saint immigrants first arrived in San Francisco in 1846. They built communities in the area as they progressed toward the Great Basin. In January 1847, the Mormon Battalion, a group of Latter-day Saints preparing to fight in the Mexican-American War, arrived in San Diego. Six Battalion members were at Sutter's Mill in January 1848, when gold was discovered.
The Church of Jesus Christ of Latter-day Saints colony of New Hope was founded in 1850. The first Church building was completed that same year. In 1851, Church leaders encouraged colonization in San Bernardino to augment a travel route from the coast for Utah-bound Saints. The land boom of the 1920s also attracted many members to California. Today, along with several temples, California has more missions than any other state. Additionally, members have cooperated to provide relief for communities after earthquakes, fires, and floods.