<Tr> <Th> Added to NRHP </Th> <Td> October 15, 1966 </Td> </Tr> <Tr> <Th> Designated NMON </Th> <Td> October 15, 1924 </Td> </Tr> <P> The Castillo de San Marcos is the oldest masonry fort in the continental United States . Located on the western shore of Matanzas Bay in the city of St. Augustine, Florida, the fort was designed by the Spanish engineer Ignacio Daza . Construction began in 1672, 107 years after the city's founding by Spanish Admiral and conquistador Pedro Menéndez de Avilés, when Florida was part of the Spanish Empire . The fort's construction was ordered by Governor Francisco de la Guerra y de la Vega after the destructive raid by the English privateer Robert Searles in 1668 . Work proceeded under the administration of Guerra's successor, Manuel de Cendoya in 1671, and the first coquina stones were laid in 1672 . The construction of the core of the current fortress was completed in 1695, though it would undergo many alterations and renovations over the centuries . </P> <P> When Britain gained control of Florida in 1763 pursuant to the Treaty of Paris, St. Augustine became the capital of British East Florida, and the fort was renamed Fort St. Mark until the Peace of Paris (1783) when Florida was transferred back to Spain and the fort's original name restored . In 1819, Spain signed the Adams--Onís Treaty which ceded Florida to the United States in 1821; consequently the fort was designated a United States Army base and renamed Fort Marion, in honor of American Revolutionary War hero Francis Marion . The fort was declared a National Monument in 1924, and after 251 years of continuous military possession, was deactivated in 1933 . The 20.48 - acre (8.29 ha) site was subsequently turned over to the United States National Park Service . In 1942 the original name, Castillo de San Marcos, was restored by an Act of Congress . </P>

When did the castillo de san marcos begin construction