Molycorp was an American mining corporation headquartered in Greenwood Village, Colorado, that specialized in the mining and processing of rare earth elements (REEs). The company operated the Mountain Pass rare earth mine in California, which was once the world’s largest supplier of rare earth elements. Founded in 1947 as a unit of Molybdenum Corporation of America, the company played a crucial role in establishing the United States as a major producer of rare earth materials during the Cold War era. The company went public in 2010 amid growing concerns about China’s dominance in the rare earth market. Following its IPO, Molycorp invested heavily in modernizing the Mountain Pass facility and expanding its operations through acquisitions, including the purchase of Neo Material Technologies in 2012. However, falling rare earth prices, increased competition from Chinese producers, and substantial debt from its expansion efforts led to financial difficulties. In 2015, Molycorp filed for Chapter 11 bankruptcy protection and subsequently ceased operations at Mountain Pass. The company’s assets were later sold off, with the Mountain Pass mine being acquired by MP Materials in 2017. Molycorp’s rise and fall highlighted the challenges faced by non-Chinese rare earth producers and the strategic importance of rare earth elements in global technology supply chains.