Castillo San Felipe del Morro

Words: Aleena Siddiqui
Photo Credits: felixairphoto, VisionsbyAtlee, and Sean Pavone



Background

Castillo San Felipe del Morro ("The Promontory Castle of Saint Philip"), or El Morro ("The Promontory"), is a colonial fort built by the Spanish in America. It was commissioned by King Charles I of Spain and built in honor of King Philip II. Its construction began in 1539 and wasn't completed until 1787. In the late 1500s to early 1600s, the structure was transformed. Juan Bautista Antonelli and Bautista Antonelli, two Italian engineers, designed the fort to hold out against cannon fire. In the late 1700s, two Irishmen sent on behalf of the Spanish, Colonel Thomas O'Daly (Chief Engineer) and Alexander O'Reilly (Field Marshal), made improvements to Puerto Rican fortifications and troops. The final significant alterations made to El Morro were completed by O'Daly. The six-level structure has 18 to 25-foot-thick walls and stands on a hill that is 140 feet high. Located in Old San Juan, Puerto Rico, the fort protects the Bay of San Juan at its entrance and faces the Atlantic Ocean. It was designed to target and fire at enemy ships. Its location was strategic, given that it stands near what was thought to be one of the best harbors in the Caribbean. By the time El Morro was complete, it was the most feared Spanish fort and considered to be unbeatable.

Attacks on El Morro
In 1595, when the fort was still incomplete, English privateer Sir Francis Drake attacked San Juan. Drake was known at the time for his attacks on Spanish ships and settlements across America. Due to strategic errors on his part, as well as the resilience of the defenders, El Morro was victorious. The attack was carried out in an attempt to weaken Spain’s power in the New World. However, this victory helped prove El Morro’s defense capability. A 1598 attack by the Earl of Cumberland, George Clifford, resulted in El Morro’s defeat. Clifford learned from Drake’s failure, preying on the landside of this structure. This area of the fort was considered its weak spot. As a result, the English obtained control over Puerto Rico. However, this only lasted for two months, as a dysentery outbreak occurred. In 1625, during the Eighty Years’ War, the Dutch attempted to take over the fort. This effort resulted in their defeat, and after 21 days, they burned the city and retreated. During their 1797 attack on Puerto Rico, the British targeted El Morro, which helped protect the city during this time. This was part of their third and final invasion of the city during the Anglo-Spanish War.

The Fort's Downfall



The technological advancements that occurred during the Industrial Revolution transformed how nations engaged in conflict. By the time the Spanish-American War of 1898 took place, El Morro was no longer able to serve its purpose due to these major changes in technology. Rear Admiral William T. Sampson commanded the U.S. Navy during the bombardment of San Juan. This occurred on May 12, 1898, and was done with the intent to establish naval dominance in this geographic location. However, the fort proved unable to withstand the powerful technology utilized by the Americans. The Spanish-American War was significant, as Spain no longer ruled over the Americas, and the United States rose as a world power. Throughout both World Wars, El Morro was utilized as a United States military base. When World War I occurred, El Morro was used to monitor naval activity, serving as a lookout point to identify enemy submarines and ships. During this war, the structure was also utilized for military communications. Anti-aircraft guns and a bunker were among the additions made to the structure during the Second World War. However, it was apparent that the fort was outdated for its initial intent.

El Morro in the Modern Day



In the late 1940s, El Morro transitioned from a military site to a historic landmark. In 1949, under the National Park Service, the fort became a new addition to the San Juan National Historic Site, which was established the same year. Another structure included on the site was Castillo San Cristóbal, an additional military fortification. The National Park Service made extensive efforts to restore and preserve El Morro. The organization also created educational programs surrounding the structure. In 1983, El Morro became a UNESCO World Heritage Site. This designation furthered global awareness surrounding the structure, resulting in increased tourism. Today, it is among the most popular tourist attractions in Puerto Rico. El Morro serves as a significant representation of the island’s history and culture, embodying the Spanish Empire’s impact on the New World. It also showcases a combination of modern engineering and medieval architecture. Overall, the site of El Morro will allow future generations to celebrate its rich Puerto Rican heritage while recognizing the structure as a longstanding symbol of resilience.
About: American Treasure
The Science of a Straight Line: Why Masonry’s Smallest Decisions Make the Biggest Differences
September 2026

There is a unique phenomenon in construction: the human eye can spot an out-of-plumb wall from 50 yards away across a crowded job site. We might not always be able to explain the exact mathematical deviation without a laser level, but our brains instantly

The Utah Masonry Council's Masonry Education Day
September 2026

The 2026 Masonry Education Day at Interstate Brick in West Jordan is bringing together members of Utah’s architecture, engineering, and construction community for a day focused on education, technical understanding, and workforce development. The event r

MCAA Upstate New York: Regaining Market Share Through Education
September 2026

The Upstate New York chapter of the MCAA was established in 2014 by a dedicated group of both union and non-union masonry contractors, producers, and suppliers who shared concerns about the declining use of masonry. T

GEN NXT: Luis Sontay
September 2026

For this month, the MCAA got to sit down with aspiring mason Luis Sontay. From taking an interest in masonry as a kid to placing 1st in a postsecondary competition, Luis’ dedication and passion for the trade is clear. Luis describes his early passion fo