The Garden Key Lighthouse at Fort Jefferson, FL in the Dry Tortugas National Park on an island and was built to replace one lost during a hurricane in 1873. It stands on 55 foot walls and is 37 feet tall. It remained operational until 1912.
In 1846 the US ARMY decided to build a fort to protect the shipping lanes in the Gulf of Mexico. The fort was built to hold 450 cannons and 1,500 troops but was never completed. Instead, it was used as a prison.