Fort Jefferson

Fort Jefferson is a large mid‑19th‑century coastal fortress on Garden Key in the Dry Tortugas, about 70 miles west of Key West, Florida. Built of brick as a coastal defence work, it was never fully completed but remains one of the largest brick masonry structures in the Americas.

The fort contains extensive casemate rooms and a surrounding moat; ranger‑led tours interpret its military construction, Civil War use and later role as a military prison. The fort and the surrounding coral reefs are the focal points for visitors who arrive by boat or seaplane from Key West.

Visitors commonly combine a fort tour with snorkeling on nearby reefs, birdwatching and limited island camping; facilities on Garden Key include a small campground and day‑use areas. The park is managed as Dry Tortugas National Park and access is regulated to protect the marine and historic resources.

Garden Key lies on a low coral outcrop in the Gulf of Mexico and is surrounded by reef habitat within a large marine park.

• Location and access: Located on Garden Key in Dry Tortugas National Park, about 70 miles (113 km) west of Key West, Florida; access is by boat or seaplane from Key West.
• Size and history: Construction began in the mid 19th century and the unfinished fort is one of the largest brick masonry structures in the Americas; it was used as a Union base during the Civil War and later as a military prison.

What to See #

• Fort Jefferson structure: The fort itself - a massive brick coastal bastion with multi‑tiered casemates and a surrounding moat, open for ranger‑led tours.
• Garden Key campground and visitor facilities: Garden Key campground and visitor areas on the island that provide day‑use picnicking, camping by permit and direct access to snorkeling sites.
• Reef and snorkel sites: Shallow reefs and drop‑off snorkel sites around the Dry Tortugas, popular for coral and fish watching directly offshore from Garden Key.