One theory on the origin of the concept comes from William Jennings Bryan's resignation as United States Secretary of State in the Wilson Administration. At the outbreak of World War I, the leading global exporter of nitrates for gunpowder was Chile. Chile had maintained neutrality during the war and provided nearly all of the US's nitrate requirements. It was also the principal ingredient of chemical fertilizer in farming. The export product was sodium nitrate, a salt mined in the northern part of Chile which is often called "Chilean saltpeter."