What is the name of the historic fort in St. Augustine, Florida, and when was it first constructed?

The historic fort located in St. Augustine, Florida is known as the Castillo de San Marcos. It was first constructed by the Spanish in 1672, making it the oldest masonry fort in the United States. The fort was built to protect St. Augustine and the Spanish treasure fleets from attack by pirates and foreign powers. The Castillo de San Marcos was constructed using coquina stone, which is a type of limestone made up of shell fragments. The unique properties of the coquina stone made it an ideal building material for the fort as it could absorb the impact of cannon fire without shattering.

Over the years, the fort has played an important role in the history of the United States. It has been attacked and sieged several times, but has never fallen to an enemy force. Today, the Castillo de San Marcos is a popular tourist attraction and is managed by the National Park Service. Visitors can explore the fort's ramparts, watch reenactments of historic events, and learn about the fort's role in American history.