The 20th century brought more industrialization; in 1904 the Los Angeles and Salt Lake Railroad built a line through the city, and in 1909 the International Smelting and Refining Company smelter was built in Carr Fork/Pine Canyon east of the city . The Tooele Valley Railway, a seven-mile line, ran from the smelter west to the Union Pacific Railroad main line. This line brought ore from various area mines to the smelter; later a 20,000 ft aerial tramway was also used to transport ore from the mine to the smelter. By 1941 a 22,000 ft tunnel had been completed through the mountain, to move ore to the smelter entirely underground. The smelter began processing copper in 1910, with lead and zinc processing commencing in 1912. In 1946 the copper smelter ceased operation, the zinc operation halted in 1968, and the lead processing was halted in 1972. The entire site was demolished during 1972–74. However, consideration was being given during this latter period to extracting ore from Carr Fork Canyon, rather than relying on the ore from the east face of the mountain range. In 1969 the mining company began exploration drilling. In 1974 a copper mine and mill ("Carr Fork Operations") was started; it began processing ore in 1979, and ran until 1981. The Tooele Valley Railway was used to haul away the scrap when the International smelter was torn down, and remained to serve the Pine Canyon mill. It was shut down and abandoned when the Pine Canyon “Carr Fork” mine and mill shut down; its last day of operation was 28 August 1982.