Castillo San Felipe del Morro, Key to the Defence of San Juan’s Harbour

By the 1500s Spain had claimed the entire Caribbean basin and, with large quantities of gold, silver and exotic spices in their Central and South American colonies, control of the Caribbean became essential to Spain’s economic interests.

Propelled by prevailing trade winds from off the African coast, Puerto Rico was the first major island with fresh water that ships encountered as they sailed west from Europe. As a protected harbour at the entrance to the Caribbean, San Juan became an important part of Spain’s strategy to protect its empire from jealous European rivals. The harbour was a secure, deep-water port and the nation that controlled it would be able to protect their merchant ships and send warships out to control shipping to and from the Caribbean.

Philip IV, King of Spain, knew the importance of the island and its port and famously wrote, “It is the forefront and vanguard of all my West Indies, and consequently the most important of them all – and the most coveted by my enemies”. The importance of San Juan for the security of the Spanish empire also impressed King Carlos III  and in September 1765 he decreed that San Juan should be made a “Defence of the First Order”.

Castillo de San Felipe del Morro was built over ten generations and almost 250 years to defend this important harbour and allowed Spain to control Puerto Rico for almost 400 years.

During the 1500s the battery and the tower that would be the basis for the fortress protected the harbour and provided refuge for some of the people of San Juan during attacks. However, over time increased threats from European rivals brought needs for increased defence. Batteries and defence work was added to the El Morro tower and later a system of walls surrounding the city were installed.

In 1765 military reforms resulted in a need for considerable renovation of El Morro. New batteries, quarters for troops and additional walls were built. By 1790 El Morro had been transformed into a powerful fortress with its defences spread across six levels and, by the end of the 1700s, San Juan’s defences were the most extensive of all of Spain’s colonies.

Weakened by international conflict and civil war during the early 1800s, Spain lost much of its once extensive American empire. A series of wars of liberation led to the independence of Mexico, Colombia, Venezuela, Argentina, Peru and Chile. By the 1870s only Cuba and Puerto Rico remained under Spanish rule.

With the decline of Spain’s imperial fortunes throughout the 1800s, San Juan’s military defences were slow to modernise. When tensions with the United States began to rise, Spain rushed to install newer models of artillery. By the time war broke out in 1898, El Morro mounted only 11 up-to-date cannons. The conflict lasted 109 days and resulted in Spain’s defeat, independence for Cuba, and the transfer of the Philippines, Guam and Puerto Rico to the United States.

Throughout World War I, El Morro’s location at the entrance to the harbour continued to serve as a key element of the port’s defences and American artillerymen would scan the horizon for hostile ships from the ramparts.

The opening of the Panama canal in 1914 made Puerto Rico strategically important to American interests in the Caribbean. Once again, the island’s location was vital to protect shipping. During World War 2 San Juan’s defences were modernised and bomb-proof command bunkers, observation towers and gun emplacements were added.

El Morro continued to house  artillery for coastal defence, however it was also used by a variety of support services. By the 1950s its grounds contained a hospital, baseball diamond, swimming pool, outdoor theatre and a golf course.


  • Information signs at Castillo de San Felipe del Morro

Castillo San Felipe del Morro, Key to the Defence of San Juan’s Harbour

by Uncover Travel time to read: 2 min
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