The first company to begin work in the Carlsbad basin was the United States Potash Company .The first shaft was started in 1929 and completed in 1931 to a total depth of 986 ft. The first carload was shipped in 1931 and consisted of manure salts containing 25% K2O. in 1932 construction of the refinery was started near the Pecos River, about 13 miles southwest of the mine. This location was selected for two reasons: it had a dependable water supply and it was close to the Santa Fe Railroad was constructed to connect the mine to the refinery. This landmark mine is still operating today and it now Mississippi Potash,Inc.'s, West mine