Denver's position near the mineral-rich Rocky Mountains encouraged mining and energy companies to spring up in the area. In the early days of the city, gold and silver booms and busts played a large role in the city's economic success. In the 1970s and early 1980s, the energy crisis in America and resulting high oil prices created an energy boom in Denver captured in the soap opera Dynasty. Denver was built up considerably during this time with the construction of many new downtown skyscrapers. When the price of oil dropped from $34 a barrel in 1981 to $9 a barrel in 1986, the Denver economy also dropped, leaving almost 15,000 oil industry workers in the area unemployed (including former mayor and current governor John Hickenlooper, a former geologist), and the nation's highest office vacancy rate (30%). The industry has recovered and the region has 700 employed petroleum engineers. Advances in hydraulic fracturing have made the DJ Basin of Colorado into an accessible and lucrative oil play. Energy and mining are still important in Denver's economy today, with companies such as EnCana, Halliburton, Smith International, Rio Tinto Group, Newmont Mining, Noble Energy, and Anadarko headquartered or having significant operations. Denver is in 149th place in terms of the cost of doing business in the United States.
State Highway 470 (C-470, SH 470) is the southwestern portion of the Denver metro area's beltway. Originally planned as Interstate 470 in the 1960s, the beltway project was attacked on environmental impact grounds and the interstate beltway was never built. The portion of "Interstate 470" built as a state highway is the present-day SH 470, which is a freeway for its entire length.