Excerpts from Books and Wikipedia
The guano boom occurred in the 1840s. "Formerly the mighty center of Spanish-speaking South America, its very name synonymous with silver, Peru had suffered a series of turbulent military caudillos in the wake of independence. But already in the 1840s, a new export product rescued Peruvian fortunes or, more precisely, the fortunes of the “decent people” of Lima. This product was guano, the old fertilizer from Inca days, seabird manure, that had accumulated for thousands of years on offshore islands where the birds nested. Easy—if not exactly pleasant—to mine, guano deposits stood in great mounds, waiting to be shoveled aboard ship, and European farmers could not get enough of the nitrogen-rich fertilizer." [Born in Blood & Fire: A Concise History of Latin America, 4th Ed., p. 157-8]