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November 19, 1493 – Puerto Rico is discovered by Europeans, by Italian explorer and colonizer Christopher Columbus on his second voyage westwards
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August 1508 – Juan Ponce de León discovered the San Juan Bay
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1537 – La Fortaleza is constructed
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1539 – Construction begins on Castillo San Felipe del Morro (El Morro)
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1582 – San Juan becomes a presidio, or military encampment
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November 22-23, 1595 – British privateer Sir Francis Drake attacked San Juan
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June 16 - August 27, 1598 – British Sir George Clifford attacks and occupies San Juan
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1601-1609 – the Spanish rebuilds parts of San Juan, reinforced El Morro and the Boquerón Battery
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1608-1610 – Wooden San Juan de la Cruz is constructed on El Cañuelo Island
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September 25 – November 2, 1625 – Dutch privateer Boudewijn Hendricksz attacks San Juan and resides in La Fortaleza. Unsuccessful in capturing El Morro, Hendrickzs collected all of the wealth from the civilian homes and burned San Juan and San Juan de la Cruz to the ground before leaving the island
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1634 – Construction began on a new fort, Castillo San Cristóbal
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1634 – Construction began on the city walls
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1650 – The entire city is encircled with a wall
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Circa 1650s – El Espigón, or la Garita del Diablo (the Devil’s Sentry Box), is constructed
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1660 – San Juan de la Cruz is rebuilt in masonry
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1660s – Fort La Perla is constructed (The modern-day barrio La Perla is built where this fort used to be!)
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April - May 1765 – Field Marshall and Inspector-General Alexander O’Reilly is brought to Puerto Rico to reform the soldiers stationed there
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1765-1790 – Colonel Thomas O’Daly and successors build a defense-in-depth system, focusing on batteries in El Morro, creation of San Cristóbal, sections of the city walls, San Gerónimo, El Cañuelo, and the Boquerón sector
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April 17 - May 1, 1797 – British General Ralph Abercrombie and Admiral Sir Henry Harvey attempt to invade San Juan from the east
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1897 – The government tears down the southeastern section of the city wall; the Santiago Gate, Ravelin, and Bastion; and parts of San Cristóbal to expand the city outside of the defensive walls
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May 12, 1898 – American Naval Fleet commanded by Admiral William T. Sampson attacked San Juan, striking the fortifications and the city walls
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July 1898 – American General Nelson A. Miles entered Puerto Rico from the south at Guánica, and intended to rendezvous at San Juan
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December 10, 1898 – Treaty of Paris signed, ending Spanish-American War and Spain cedes Puerto Rico, Guam, and the Philippines to the United States
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1898 – Fort Brooke established by the U.S. Army at El Morro
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1949 – El Morro and San Cristóbal were transferred from the United States Military to the Department of the Interior, National Park Service
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1983 – United Nations Educational, Scientific, and Cultural Organization (UNESCO) identifies La Fortaleza and San Juan National Historic Site as a UNESCO site