Castillo de San Marcos

The Castillo de San Marcos is the oldest masonry fort in the United States. Located on the shore of Matanzas Bay in the city of St. Augustine, Florida, construction was begun 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.

After Britain had gained control of Florida in 1763 as part of the Treaty of Paris (1763) - in exchange for Havana, Cuba - which they had captured from Spain - St. Augustine became the capital of British East Florida, and the fort was renamed Fort St. Mark until the signing of the Treaty of Paris (1783) when Florida was transferred back to Spain.

In 1819 Spain signed the Adams-Onis 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.

Castillo de San Marcos has withstood siege by British forces led by the governor of the Carolina Colony James Moore, in 1702 and Georgia's colonial governor James Oglethorpe in 1740. Possession of the fort has changed six times 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), with each transfer being without force.

Under United States control the fort was used as a military prison to incarcerate members various of 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 Cheyenne.

Castillo de San Marcos 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 site was turned over to the United States National Park Service.