The name of this massive fortress is “Castillo de San Felipe del Morro”, which means “Castle of St. Philip of the Headland”. Named after the patron saint King Philip II of Spain (1556-1598), it is the older one of two great forts that served as quarters for San Juan’s land and naval forces.
The earliest military structure on this headland was a round stone tower, which resembled the chess piece known as a “rook” or “castle”. Built in 1539-40, it used to be the only defence structure protecting the entrance to San Juan harbor. This tower, which was so small that only four cannons could be mounted thereon, exists to this day. But as it has been incorporated into El Morro’s Santa Bárbara Bastion, it can only be seen from the inside. When the U.S. Navy bombarded San Juan in 1898, a shell penetrated El Morro and remained in the tower wall. Fragments of the shell can still be seen inside the wall, a visible reminder of the Spanish-American War in Puerto Rico.
Approaching El Morro from the land side, the fort strikes the observer as being set very low into the ground, thus forming a marked contrast to its dramatic appearance as seen from the sea side. Such a low fort profile is typical of military constructions of the 16th to 18th centuries, when fortresses were designed in such a way as to offer as small a target as possible to the cannons of the besiegers. By digging a dry moat along the entire length of the landward side of El Morro, the main wall could be sunk low into the ground while still maintaining a considerable height from base to parapet. In this way, any attempt to scale the walls could be effectively frustrated. The moat itself constitutes yet another obstacle, which any attacker would have to overcome in order to take the fort.
The three lighthouses were located on El Morro’s sixth level. The first one was constructed in 1846 to be subsequently replaced by the second one in 1876, while the third one was erected in 1899-1900. The El Morro lighthouse took a direct hit during the Spanish-American War bombing, but the brick foundation was recovered and used for the construction of the lighthouse which is in use today. This aid to navigation still helps ships to enter San Juan harbor, one of the busiest ports of the Caribbean.