Mining opened Arizona to Anglo-American settlement and subsequently led to its statehood, though mining in Arizona began with the Spanish discovery of the rich Planchas de Plata silver deposits just west of Nogales in 1736. In the century that followed, Spanish miners opened numerous mines around Tubac, Patagonia, Ajo and Arivaca. After the California gold rush subsided, many prospectors, hearing stories of Arizona's mineral wealth, turned eastward. The latter half of the 19th century brought a series of booms and busts as new mineral deposits were discovered and worked out. Although gold and silver were the initial enticement, copper eventually became the state's most important mineral. The richest silver strike in Arizona occurred in southeastern Arizona, east of Fort Huachuca, in 1877, and a short time later the town of Tombstone was founded there. Within two years, Tombstone was the largest town in the territory and had several neighboring mill towns supporting the mines, but by 1888 the boom had ended because groundwater limited the depth of the mines. Tombstone remains active today, with many of its historic buildings and sites preserved for visitors.