Why did Chilean saltpetre become important in the 19th century?

Chilean saltpetre, or sodium nitrate, became critically important in the 19th century primarily due to its role in industrial and military applications. Following the discovery of massive deposits in the Atacama Desert, it became a vital global commodity.123

Its significance was driven by several key factors:

• Explosives Manufacturing: While potassium nitrate was traditionally used for black powder, it was expensive and limited in supply. In 1858, industrialist Lammot du Pont developed a method to use sodium nitrate for blasting powder. Although it was less stable than potassium-based powder, it was significantly cheaper and highly effective for mining and construction projects.1
• Economic Dominance: Chile held a near-monopoly on these nitrate deposits, which became a primary source of national wealth. Export taxes on the mineral accounted for half of the Chilean government's revenues, and the industry attracted significant foreign investment, particularly from Britain.243
• Agricultural and Industrial Use: Beyond explosives, it became essential for the nitric acid industry and served as a major fertilizer for agriculture.5

The strategic value of these mines was so high that it fueled the War of the Pacific (1879–83), as Chile sought to secure control over the nitrate-rich territories of Tarapacá and Antofagasta.246