Ansel Adams captured Taos Pueblo (left) in this photograph from the National Archives. Sunlight filters between trees in Redwood National Park (right) photograph courtesy of the National Park Service.
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World Heritage Sites in the United States

San Juan National Historic Site
San Juan, Puerto Rico
San Juan National Historic SiteSan Juan National Historic Site is a World Heritage Site in Puerto Rico.
National Park Service

The main elements of this World Heritage Site, found within San Juan National Historic Site, consist of La Fortaleza; the three forts of San Felipe del Morro, San Cristóbal, and San Juan de la Cruz (El Cañuelo); and a large portion of the City Wall, built between the 16th and 19th centuries to protect the city and the Bay of San Juan. They represent a fine display of European military architecture adapted to harbor sites on the American continent.

These fortifications are characteristic examples of the historic methods of construction used in military architecture over this period, which adapted European designs and techniques to the special conditions of the Caribbean port cities. La Fortaleza -- founded in the early 16th century and considerably remodeled in later centuries -- reflects developments in military architecture during its service over the centuries as a fortress, an arsenal, a prison, and residence of the governor-general and today the governor of Puerto Rico.

The principal components of this defensive system include:

  • La Fortaleza, founded in 1530-40, served as an arsenal, prison, and residence for the Governor-General of the island.
  • El Morro, built to protect San Juan Bay, developed into a masterpiece of military engineering with stout walls, carefully planned steps and ramps for moving men and artillery.
  • San Cristóbal, with its dependencies, is another accomplished example of the military architecture of the second half of the 18th century.
  • La Fortaleza and San Juan National Historic Site represent the continuity of more than four centuries of architectural, engineering, military, and political history.

During the 16th century, recognizing the need to protect the Spanish treasure fleets on their voyages to and from the New World, the Spanish erected vast fortifications throughout their territories in the Caribbean Islands and the Gulf of Mexico. Designated a World Heritage Site, the Spanish system of fortifications in San Juan, Puerto Rico is the oldest European construction in territory of the United States and one of the oldest in the New World. These fortifications guarded the entrance to the Bay of San Juan, helped the Spanish maintain sovereignty over Puerto Rico, and protected Spanish commerce in the Caribbean basin. The forts and three miles of city wall are fine examples of military architecture reflecting the power and glory of the Spanish Empire and the beginning of European ascendancy in world affairs.

Constructed between 1533 and 1540, La Fortaleza consisted of a circular tower and four massive stone walls. In 1846, La Fortaleza was enlarged and its street façade altered. The original tower, now called Torre del Homenaje, or tower of homage, still stands; its name derives from an island tradition in which the resident governor climbs to the top of the tower to pledge a solemn oath of loyalty and courage during dangerous times. Today, the building, at one time designated the Spanish Captain-General of Puerto Rico's official residence, serves as the official residence and offices of Puerto Rico's Governor.

View of San Juan Harbor from the
San Juan National Historic Site
National Park Service

The Spanish began construction of a stronger and more efficient fortification for the protection of the city’s anchorage at the entrance of the San Juan harbor in 1539. Castillo de San Felipe del Morro has a round masonry tower and resembles a castle.

Castillo de San Cristobal, which dates from 1634, was part of the new defense line to protect San Juan against land approaches coming from the east.  The Spanish erected the fortification on the northeastern edge of San Juan, which was 150 feet above sea level and a mile away from the headland where El Morro stood.

In 1678, King Charles III--who had designated San Juan as the defender of the first order--sent two Irishmen to strengthen the city’s fortifications and defense lines. By the end of the 1780s, Thomas O’Daily and Alexander O’Reilly had rebuilt El Morro, San Cristobal, and the defense wall into its present day image, thus transforming San Juan into the most powerful stronghold in America.

With the new upgrades, San Cristobal became the largest Spanish fortress in the New World with 450 canons and expanding over 27 acres of land. The Irish engineers designed the defense system on the principle of “defense in depth,” which meant that enemies would have to break several barriers--that were each higher and stronger than the one before them—to besiege the fort.

For the explorers and colonists of the New World who came from the east, Puerto Rico was an obligatory stopping-place in the Caribbean. This was the start of its primordial strategic role at the beginning of the Spanish colonization. For centuries, the island was a stake disputed by the Spanish, French, English and Dutch. The fortifications of the Bay of San Juan, the magnificent port to which Puerto Rico owes its name, bear witness to its long military history. San Juan had the first municipal government in the New World outside Santo Domingo, as well as the first military presidios in Spanish America. By the 19th century, the old city had become a charming residential and commercial district. The city itself, with its institutional buildings, museums, houses, churches, plazas and commercial buildings, is part of the San Juan Historic Zone which is administered by municipal, State and Federal agencies.

At the San Juan National Historic Site visitor center, visitors have the opportunity to participate in ranger-led orientation talks about the fortifications and to see the film, "The Fortifications of Old San Juan." Programs are available in English and Spanish. Afterwards, park visitors can explore the fortifications, enjoy the beautiful natural setting and enjoy the historic city of San Juan.

Plan your visit

San Juan National Historic Site, a World Heritage Site and a unit of the National Park System, is located at 501 Norzagaray St., San Juan, PR. Click for the National Register of Historic Places file: text and photos. La Forteleza is also a National Historic Landmark. Click here for the La Fortaleza National Historic Landmark registration file: text and photos. La Fortaleza is open 8:00am to 3:00pm on weekdays. For more information, call 787-721-7000. Castillo de San Cristobal and Castillo San Felipe de Morro are open daily from 9:00am to 6:00pm, except on Thanksgiving, Christmas Day, and New Year’s Day. For more information, visit the National Park Service San Juan National Historic Site website or call 787-729-6960.

San Juan National Historic Site is also featured in the National Park Service American Latino Heritage Travel Itinerary, the Historic Places in Puerto Rico and The Virgin Islands Travel Itinerary, and the Places Reflecting America’s Diverse Culture Travel Itinerary. San Juan National Historic Site is the subject of an online lesson plan, The Forts of Old San Juan: Guardians of the Caribbean. The lesson plan has been produced by the National Park Service’s Teaching with Historic Places program, which offers a series of online classroom-ready lesson plans on registered historic places. To learn more, visit the Teaching with Historic Places website.

Many components of San Juan National Historic Site have been documented by the National Park Service’s Historic American Buildings Survey, including La Forteleza, the Castillo de San Felipe de Morro’s Lighthouse, the Castillo de San Cristobal’s Entrance Gate, Northeast Gate, South Gate, Guardhouse, and the Troops Quarters. San Juan National Historic Site has also been documented by the National Park Service’s Historic American Buildings Survey.

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