Statement of Significance (as of designation - October 9, 1960):
The first defense of San Juan, La Fortaleza was built by the Spanish in the 16th century to guard against attack by French, English, and Dutch pirates. Largely burned by a Dutch force in 1625, it was rebuilt and enlarged within 15 years. It has surved as the residence of the island's Governors for more than 400 years. Listed, along with San Juan National Historic Site, on UNESCO's World Heritage List, December 6, 1983.