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This Red-Shouldered hawk was hanging out by our bird feeders looking for a free lunch.

This Red-Shouldered hawk was hanging out by our bird feeders looking for a free lunch.

In May 1829, Commodore John Rodgers stopped at the Dry Tortugas to evaluate the anchorage. Rogers was delighted with what he found. The Dry Tortugas, he reported, consisted of 11 small keys and surrounding reefs and banks, over which the sea broke. There was an outer and an inner harbor. The former afforded a safe anchorage at all seasons, and was large enough to let a large number of ships ride at anchor. Of more importance, the inner harbor combined a sufficient depth of water for ships-of-the-line, with a narrow entrance of not more than 120 yards (110 m). Rogers said that if a hostile power should occupy the Dry Tortugas, United States shipping in the Gulf would be in deadly peril, and "nothing but absolute naval superiority" could prevail. However, if occupied and fortified by the U.S., the Dry Tortugas would constitute the "advance post" for a defense of the Gulf Coast.

The design of Fort Jefferson called for a three-tiered six-sided 420 heavy-gun fort, with two sides measuring 325 feet (99 m), and four sides measuring 477 feet (145 m). The walls met at corner bastions, which are large projections designed to allow defensive fire along the faces of the walls they joined. The heavy guns were mounted inside the walls in a string of open casemates, or gunrooms, facing outward toward the sea through large openings called embrasures. Fort Jefferson was designed to be a massive gun platform, impervious to assault, and able to destroy any enemy ships foolhardy enough to come within range of its powerful guns.

Dry Tortugas National Park preserves Fort Jefferson and the Dry Tortugas section of the Florida Keys. The park covers 101 mi2 (262 km2), mostly water, about 68 statute miles (109 km) west of Key West in the Gulf of Mexico.

Dry Tortugas is famous for abundant sea life, colorful coral reefs and legends of shipwrecks and sunken treasures. The park's centerpiece is Fort Jefferson, a massive but unfinished coastal fortress. It is the largest masonry structure in the Western Hemisphere, and is composed of over 16 million bricks. The park has almost 80,000 visitors each year. The park is accessible only by seaplane or boat.