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After the Guano Ran Out

Nitrate and phosphate mines were discovered on land around the same time that the guano islands were depleted

Potosi, a German nitrate ship
Courtesy of Langdon Maritime Photograph Collection, Division of Work & Industry

Peruvian guano from the Chincha Islands was the gold standard for natural fertilizers. Nearly two hundred feet deep in the early 1840s, it was mined out by the late 1870s.
However, by the mid-19th century, inland nitrate and phosphate mines had been discovered in Peru and Chile, as well as in North America and Europe. These finds permitted blending of the various minerals for balanced synthetic fertilizers. Some of these mines remain in use today.
Today, the United States retains ownership of several remote Pacific and Caribbean islands first claimed in the mid-19th century for the guano trade.
Nitrate Voyage Track Chart, 1914
The German “Flying P” line of merchant sailing ships made dozens of voyages from Hamburg, Germany, to the nitrate mines of Chile. Nitrates were used both for fertilizer and for gunpowder.
This chart tracks the final voyage of the German nitrate ship Potosi. When it arrived at Valparaiso, Chile, the vessel was detained for the duration of World War I. The crew disabled the ship to prevent its use by the Allies and it never sailed again.
Gift of J. Ferrell Colton