The fortress is situated approximately 6 kilometers from the border with Costa Rica, at the Raudal del Diablo rapids of the San Juan River.

[3] Martin Estete, a citizen of Granada, finally discovered the outlet of Lake Nicaragua in 1528 and named it the Río San Juan.

Captain General Fernando Francisco de Escobedo, who was also at that time Governor of Yucatán, visited the area from January – February 1673.

Construction of the fortress, initially named Fortaleza de la Limpia Pura e Inmaculada Concepción, was begun on March 10, 1673, and completed in 1675.

On the morning of July 26, 1762, a combined British and Miskito Sambu expeditionary force laid siege to the fortress in what would later be called the Battle for the Río San Juan de Nicaragua.

The garrison commander, Lieutenant Colonel Don José de Herrera y Sotomayor, had died unexpectedly on July 15,[8] only 11 days earlier.

[1] After Spain entered the American Revolutionary War in 1779, Major General John Dalling, the British governor and commander-in-chief of Jamaica, proposed a second expedition to Nicaragua.

The goal was to sail up the San Juan River to Lake Nicaragua and capture the town of Granada, which would effectively cut Spanish America in half as well as provide potential access to the Pacific Ocean.