In the late 19th and early 20th centuries, everyone wanted sodium nitrate, a white, powdery compound used in agricultural fertilizers and explosives. Turned out Chile's Pampa desert contained the world's largest saltpeter deposit. (Note: Chile saltpeter or sodium nitrate should not be confused with ordinary saltpeter, which is potassium nitrate.) Once this was uncovered, more than 200 saltpeter works were quickly constructed in the region, and thousands of workers poured in. The saltpeter works produced great wealth for Chile [sources: Strochlic, UNESCO].
But nothing lasts forever. The mines boomed from about 1870 to 1930, until the less-expensive synthetic sodium nitrate was created. By the late 1950s, the mines and company towns were abandoned. Some families fled, not even taking their clothes or household furnishings [source: Strochlic].
Today, two especially well-preserved sites remain: Humberstone and Santa Laura. Tourists heading to Santa Laura will find industrial buildings and equipment, such as the old administration house, a leaching shed and a saltpeter grinder; the latter two are the only intact ones left in the world. Humberstone is home to the workers' former homes, plus public spaces and communal buildings. In addition, you can see remains of the railway line linking the two towns as well as the old saltpeter works. In 2005, UNESCO placed the Humberstone and Santa Laura Saltpeter Works on its World Heritage Site list for their "exceptional testimony to technological progress and global exchanges which were the cornerstone of the industrial era" [source: UNESCO].