Castillo de San Marcos National Memorial

The Castillo de San Marcos, built 1672-1695, served primarily as an outpost of the Spanish Empire, guarding St. Augustine, the first permanent European settlement in the continental United States, and also protecting the sea route for treasure ships returning to Spain. The Castillo was made a National Monument in 1924 and became part of the National Park system in 1933. The park consists of the original historic Castillo fortress itself with its attendant grounds, some 25 total acres.