 In 1898, he became a U.S. citizen.Loeb vertically integrated the company by expanding into the ownership of smelting and refining facilities while securing his supply of raw materials by signing exclusive contracts with large mines to purchase their entire output; and then processing them at AMCO-owned facilities.He also expanded AMCO's activities into Mexico with investments in lead, silver and zinc mining first as an agent for its parent Metallgesellschaft and later as a direct investor during World War I.