(1980s) The tour was officially dedicated on June 29, 1968. By mid-August, an additional $4,625 was spent on promotion to attract visitors. When the tour season ended on Oct. 27, 1968, a total of 15,499 people -- 50 percent of those from out of state -- visited the active mine. In 1969, the tour opened from May to October on weekends and holidays. A total of 18,643 admissions were counted in 1969.