A history of the Questa molybdenum (MOLY) mines, Taos County, New Mexico
— John. Schilling

The true nature of the molybdenum-bearing veins in Sulphur Gulch (a tributary of the Red River, 8 km east of Questa) was recognized in 1916. Several attempts were made to develop and mine the veins. In 1919, Molybdenum Corp. of America acquired the property and continued development-mining. In 1923, a mill and a camp were built along Red River, and production soared. Ore was extracted by following veinlets down-dip and laterally. Any ore-pockets encountered were stoped, hand-sorted, and the molybdenite was concentrated by flotation. By 1941, the mine extended so deep (260 m) that a mile-long tunnel was driven north from Red River Canyon to connect with the deepest workings. Haulage, drainage, and ventilation costs were greatly reduced. Mining continued down-dip for another 75 m (250 ft) before the high-grade ore ran out. Underground mining ceased in 1958, but exploratory drilling and drifting, begun in 1956, continued. By 1964, a large tonnage of low-grade, open-pitable ore had been delineated just west of the underground mine. The old camp was torn down; a large, modern mill was built on the camp site, and pre-mining stripping began. Openpit mining began in 1965 and continued until 1981. In 1975, exploratory drilling discovered a large orebody beneath the open-pit mine that extended W-SW from the pit. This "deep" ore was developed by vertical shafts and a 2130-m-long (7000 ft), 10-degree decline from the mill to the orebody. Once again the mill was renovated and enlarged, and underground mining began in 1983. The ore is block-caved, hauled up the decline and milled. A soft molybdenum market forced the mine to shut down in 1986. Prices have since improved, and the mine was reopened in 1989. Through 1989, over 190 million pounds of MoS₂ have been produced.