Castillo de San Marcos is the oldest existing permanent seacoast fortification in the continental United States. The present star-shaped fort, surrounding moat, and earthworks were constructed between 1672 - 1756 to protect Spanish territory in Florida and the shipping routes along the Florida coast. Castillo de San Marcos replaced an earlier series of earth and wood fortifications and was the northernmost outpost of the Spanish Caribbean. It was the focus of the struggle between Great Britain and Spain for regional supremacy during the 17th and 18th centuries and was the site of a British garrison during the American Revolution. The fort was last employed for defensive purposes in 1898 during the Spanish-American War.
Castillo de San Marcos National Monument, administered by the National Park Service, is at 1 Castillo Drive in downtown St. Augustine. Open daily 8:45 a.m. - 4:45 p.m. Admission. For more information visit the National Park Service's website, Castillo de San Marcos National Monument.