It is the only fort in the U.S. that has served as a Revolutionary War site, a Civil War prison, and an active coastal defense fortification.
The site was the location of the largest bombardment in the Revolutionary War, with the British firing over 10,000 shells in a single day.
The fort's design includes bomb-proof casemates built to withstand heavy naval artillery fire.
It is listed as a major historic landmark despite being positioned directly under the flight path of Philadelphia International Airport.
The fort served as a munitions depot during World War II.
In the 19th century, the site was nicknamed 'The American Bastille' while serving as a prison for Confederate soldiers.
The defensive walls were significantly reinforced in the 1840s using heavy granite blocks that are still visible today.
Archaeological digs at the site have uncovered thousands of artifacts, including personal effects from soldiers dating back to the 1770s.
Fort Mifflin, established in 1771 as Mud Island Fort, remains the only intact Revolutionary War battlefield in the United States. Located on the Delaware River, it played a critical role in the 1777 defense of Philadelphia by holding off the British Navy for six weeks. The site features original casemates, a commanding officer’s house, and defensive ramparts. It was designated a National Historic Landmark in 1915. During the 19th century, the structure was repurposed as a Civil War prison and a barracks for the United States Army. The fort's defensive architecture was designed by French engineer Louis-Lebeque Duportail. Today, it functions as a living history museum managed by the Fort Mifflin on the Delaware advisory council. Visitors can access various restored buildings that showcase military life across multiple centuries of American history.
The top of the stone ramparts offers panoramic views of the Delaware River with the historic architecture in the foreground.
Bring insect repellent as the proximity to the Delaware River and marshy grounds results in high mosquito activity.
Wear comfortable, sturdy walking shoes as the grounds are uneven, featuring gravel paths and historic masonry.
Check for special programming like cannon firing demonstrations or evening ghost tours before your visit.
Attempting to reach the fort on foot or by public transit, as there are no pedestrian-friendly routes through the surrounding industrial and airport zone.
The site is typically closed to the public on Mondays and Tuesdays and operates seasonally from spring through autumn.
Respect all roped-off preservation areas and refrain from climbing on original historic stone walls.
