After several unsuccessful attempts, he was introduced to several Cincinnati, Ohio, investors by Heintzelman. On March 24, 1856, US$2 million was secured to found the Sonora Exploring and Mining Company with Heintzelman as company president and Poston as managing supervisor. The company set up headquarters in Tubac, Arizona, and began mining operations in the nearby Santa Rita Mountains and elsewhere.
After multiple unsuccessful attempts, he was connected with several investors in Cincinnati, Ohio, by Heintzelman. On March 24, 1856, US$2 million was secured to initiate the Sonora Exploring and Mining Company with Heintzelman as president and Poston managing its activities.