Coal fields west of the Henrys were worked intermittently from the time the first was opened in 1888 until about 1945, when the difficulties of getting the coal to markets caused their closure. The only mineral that ever has been mined in large quantities in the Henrys is uranium. Mines were first opened in the decade just before World War I, when radium was found to be useful for medical treatments and luminous paint. Exploration for and production of uranium faltered until after world War II. In the late 1930s and during World War II, small amounts of vanadium (which occurs with uranium and was required for tempering steel) were mined in the Henrys. After the war, with the demand for uranium for nuclear weapons, many other uranium deposits throughout the Henrys were prospected and mined, and some of them are still worked today. South of the Henrys, the small settlement of Ticaboo, with a mill and company town, was built in the late 1970s to process uranium from nearby mines. By the time the town and mill were completed, however, the price of "yellowcake" (processed uranium ore) had dropped and the mill was shut down. Today, rusting machinery, abandoned shafts, and scattered debris are all that survive as relics of the uranium booms of the 1950s.