The Rama tribe lived here before the Spanish arrived, and some remain in Indio-Maíz reserve and on a small island in Bluefields Bay. From 16th-century Granada, the Europeans sent down several expeditions, hoping the river may lead to the sea. The rapids at Río Sábalo thwarted several missions, until finally the Caribbean was reached in 1539 by an intrepid soldier named Alonso Calero. It happened on St. John the Baptist's feast day; thus the river's name. The river became the main conduit to carry all of the Spanish Empire's plunder from the Pacific side of its Central American territories. Gold, silver, and indigo were just some of the commodities that sailed east, and Granada became wealthy and prosperous because of its strategic location. It was a prosperity coveted by other nations. The French and English sent constant raiding parties to take the spoils, and the river's history is a fascinating catalogue of pirate raids and colonial sieges. Mark Twain sailed down this "earthly paradise" on his way to New York from San Francisco, a passenger on Vanderbilt's inter-oceanic steamship service. William Walker made a stand at San Carlos, as did the Contras further downriver during the counter-revolution in the 1980s. Nicaragua and Costa Rica have had countless diplomatic spats over who owns the river, most recently in 2010, when Google Maps mistakenly gave Nicaragua an extra 2km (1 1/4 miles) of turf, an act that raised the hackles of the Costa Ricans and threatened a military confrontation between both countries. With its beauty and natural wealth, you can understand why the Rio San Juan is so coveted. Perhaps the most shocking is the fact that this stretch of paradise was the waterway that came very close to being the Nicaraguan version of the Panama Canal. Imagine: Instead of giant silver tarpon fish, we would have giant, rusty oil tankers with not a howler monkey or parrot in sight. Thank God for no progress.

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