Castillo De San Marcos

The Castillo de San Marcos is the oldest masonry fort in the continental United States (Castillo San Felipe del Morro in San Juan, Puerto Rico is older). Located on the shore of Matanzas Bay in the city of St. Augustine, Florida, 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 construction began at the command of Francisco de la Guerra y de la Vega after after the destructive raid of Robert Searles.

After 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. In 1819 Spain signed the Adams–Onís Treaty which ceded Florida to the United States in 1821 and the fort became a United States Army base which was renamed Fort Marion, in honor of American Revolutionary War hero Francis Marion. In 1942 the original name, Castillo de San Marcos, was restored by an Act of Congress. The fort was declared a National Monument in 1924 and after 251 years of continuous military possession, the fort was deactivated in 1933 and the 20.48-acre (8.29 ha) site was turned over to the United States National Park Service.

Castillo de San Marcos was twice besieged: first by English colonial forces led by Carolina Colony Governor James Moore in 1702, and then by Georgia colonial Governor James Oglethorpe in 1740. Possession of the fort has changed six times, all peaceful, amongst four different governments: the Spanish Empire, the Kingdom of Great Britain, the Confederate States of America and the United States of America (Spain and the United States having possession two times each).

Under United States control the fort was used as a military prison to incarcerate members of various Native American tribes starting with the Seminole - including the famous war chief Osceola - in the Second Seminole War - and members of various western tribes including Geronimo's band of Chiricahua Apache. The Native American art form known as Ledger Art had its origins at the fort during the imprisonment of members of the Plains tribes such as Howling Wolf of the Southern Cheyen.