Neglect during World War II and a subsequent decade of underfunding left the monument in poor condition but the Mission 66 program paid for the construction of much needed infrastructure, including the visitor center at Twentynine Palms, which was completed in 1963. In 1966, the NPS acquired the property of Bill Keys while allowing him to continue living at his home. He would assist with the monument's interpretation program until his death in 1969. In 1973, Gram Parsons, a member of the Byrds and the Flying Burrito Brothers, died of a drug overdose at the Joshua Tree Inn and his body was illegally burned near Cap Rock to fulfill his wish of having his ashes scattered there. Between 1975-1976, the Ryan House and Lost Horse Well, Barker Dam, Cow Camp, Keys Desert Queen Ranch, Wall Street Mill, and Desert Queen Mine were added to the National Register of Historic Places. In 1976, Public Law 94-567 designated 429,690 acres of Joshua Tree National Monument as wilderness. That same year, the Federal Land Policy and Management Act and the Mining in the National Parks Act made mining in the monument economically infeasible and the few remaining active mines ceased production. Over 300 abandoned mines were later counted within the future park area. By 1977, the NPS reduced the non-federal land in Joshua Tree to 11,470 acres through purchases, exchanges, and takings. In 1981, Kaiser Steel, Inc. closed its steel mill at Fontana and the Eagle Mountain Iron Mine. In 1984, Joshua Tree National Monument, Death Valley National Monument, Anza-Borrego Desert State Park, and the Santa Rosa Mountains Wildlife Management Area were designated as the four core areas of the Mojave and Colorado Deserts Biosphere Reserve. The following year, a native plant nursery was added to the Joshua Tree headquarters to build a stock of plants for the rehabilitation of disturbed areas.