During the California Gold Rush, Livermore made no attempt to join the miners. Instead, in 1847 he and Noriega had purchased Rancho Cañada de los Vaqueros and added it to their holdings. Their lands were on the route from the southern San Francisco Bay Area to the gold fields and so, a post office was established there in 1851, operating for two years. He was known for his generosity and hospitality to passers-by, so much that the area became known as "Livermore's Valley". When Alameda County, California, was formed in 1853, Livermore was appointed supervisor of roads in the county. In 1854 he purchased Noriega's half of Rancho Las Positas and deeded his half of Rancho Cañada de los Vaqueros to Noriega.