Julia (Julie) Villiers Lewis McMillan Penrose (1870–1956) was a wealthy American philanthropist born to a prominent family, the wife of the James (Jim) McMillan until he died in 1902, then the wife of millionaire Spencer Penrose until his death in 1939. Julie's giving during her marriages, contributions to the region around her, and the state of Colorado, continued even after death with the creation of the perpetual El Pomar Foundation.

Spencer Penrose was an American entrepreneur and philanthropist. He made his fortune from mining, ore processing, and real estate speculation in Colorado and other parts of the West. He founded the Utah Copper Company in 1903, and also established mining operations in Arizona, New Mexico and Nevada.