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The History

Of Fort Mifflin

History LIVES at Fort Mifflin! Experience history first-hand at National Historic Landmark Fort Mifflin – one of the only intact Revolutionary War battlefields and the only fort in Philadelphia!

Events throughout the year highlight the Fort’s long service to the United States featuring uniformed or period attired interpretive guides and reenactors. In one visit to Fort Mifflin, a guest stands on a Revolutionary War battlefield, inside a Civil War prison and next to a magazine storing gunpowder during World War II. Extraordinary – and real.

As the British marched triumphantly into Philadelphia during the last days of September in 1777, a strategic dilemma faced General William Howe, commander of the army. Surrounded by rebel forces from the north, east and west, his troops were in desperate need of supplies—gunpowder, clothing, food, and munitions. Without these items the capture of Philadelphia might become meaningless and the British would be unable to pursue and destroy Washington’s Army before winter.

South of Philadelphia in the Delaware Bay sat a fleet British ships carrying the army’s much needed supplies. General Howe gave orders to sail the fleet up the river to provide new provisions to his occupying troops.

The Americans had secured a British built fortification, sitting on Mud Island, just below the city and across the river from New Jersey’s Fort Mercer in 1775. By the fall of 1777 approximately 200 men were garrisoned at this fort, now known as Fort Mifflin, charged with the duty of holding the British off “to the last extremity” so that Washington and his exhausted army could successfully move into winter quarters.

It was here, on the frozen, marshy ground within the walls of a stone and wood fort, the American Revolution produced a shining moment. Cold, ill and starving, the young garrison of (now) 400 men at Fort Mifflin refused to give up. The valiant efforts of the men at Fort Mifflin held the mighty British Navy at bay providing Washington and his troops time to arrive safely at Valley Forge where they shaped a strong and confident army. This battle escalated into the greatest bombardment of the American Revolution and one that many say changed the course of American history.

For nearly six weeks in the fall of 1777, American troops in Fort Mifflin and Fort Mercer frustrated British naval attempts to re-supply their occupying forces in Philadelphia. Early in the morning on November 10, 1777, the British took definitive action to reach Philadelphia via the Delaware. Daybreak brought a rain of cannon fire upon Fort Mifflin beginning the largest bombardment of the Revolutionary War.

Under the direction of French Major Francois de Fleury, an engineer and tireless worker, the Americans worked each night to repair the damage of the day.

On November 15th, finally clear after days of rain and high tides, the British sailed the Vigilant and the Fury, with nineteen cannon up the back channel to the west of Fort Mifflin. In the main channel of the Delaware three ships armed with 158 cannon anchored directly offshore of the fort, while to the east three additional ships armed with 51 cannon completed the naval assault.

Against this show of force, Fort Mifflin could respond with only ten cannon. It was reported that during one hour, 1000 cannon balls were fired at the fort. As the battle progressed, British Marines climbed to the crow’s nest of the Vigilant and threw hand grenades at the soldiers in the fort.

Exhausted, cold and out of ammunition, Major Simeon Thayer evacuated Fort Mifflin’s garrison to Fort Mercer with muffled oars after nightfall on November 15. Forty men remained at the fort and set fire to what was left before making their way across the Delaware to join their comrades. They crossed to New Jersey around midnight leaving Fort Mifflin ablaze, but the flag still flying.

Repairs on the aging Mud Island Fort completed in 1863, returning Fort Mifflin to active service once again. However, rather than serve as a coastal defense fort, Fort Mifflin took on a new role: military prison.

A breakdown in prisoner exchanges between the Union and Confederacy in 1863 forced both sides to find places to hold thousands of prisoners. To handle the large influx, many different buildings, including tobacco plants, civilian prisons, and coastal forts such as Fort Mifflin, Fort McHenry in Baltimore, and Governors Island in New York, were converted to hold military prisoners. During the course of the war, over 150 prisons in the USA and CSA held over 400,000 people.

Fort Mifflin held three kinds of prisoners: Confederate prisoners of war, Union soldiers, and civilians. The prisoners were held in the Fort’s three largest casemates or bombproof shelters.

In July 1863, Fort Mifflin began receiving Confederate prisoners of war captured during the Battle of Gettysburg (July 1-3, 1863). At its peak, there were as many as 216 Confederate POWs held in the Fort’s largest casemate. Their stay at Fort Mifflin was temporary and many were transferred to larger prisons, such as nearby Fort Delaware, or released after taking an oath of allegiance to the United States.

During the Civil War, Union soldiers could face a variety of punishments for violations of military conduct, including desertion, insubordination, and dereliction of duty. Common punishments included whippings, being branded with a hot iron, and being hung by one’s thumbs. Soldiers sentenced to prison time were often forced to perform hard labor with an iron ball and chain attached to their ankle. Union prisoners stayed in one of the large casemates. There several attempted escapes, including an attempt at a mass uprising in December 1863 and a failed tunnel escape in February 1864.

The most famous (or infamous) of Fort Mifflin’s prisoners was William H. Howe, a Union private from Perkiomenville, PA, who served in the 116th Pennsylvania Volunteer Regiment. In December 1862, suffering from “inflammation of the bowels,” Howe left his regiment in Virginia and returned home to Pennsylvania. On June 21, 1863, three enrolling officers came to arrest him at his home. A gunfight ensued and one of the officers—Abraham Bertolet—was fatally wounded by a gunshot to the chest. Howe was later arrested and charged with desertion and murder. A military court found him guilty and he was sentenced to death by hanging. During his trial he was held at Fort Mifflin in an underground cell (known today as Casemate 11), and he was executed at Fort Mifflin on August 26, 1864, the only prisoner known to be executed at the Fort during the Civil War.

Among the civilian prisoners held at the Fort were forty-four citizens from Columbia County, PA, who were held in suspicion of being involved in a conspiracy to lead an armed uprising (an alleged plot known as the “Fishing Creek Confederacy”). They were held in one of the Fort’s casemates without charge or trial until October 17, 1864. After the trial all but seven were released; the rest remained held at the Fort, until receiving presidential pardons in 1864 and 1865. Some stayed until several months after the war ended.

Conditions at Fort Mifflin were poor, as was the case with many military prisons used during the Civil War. The casemates were poorly-ventilated and damp. The barracks lacked sufficient windows (many of the window sashes were rotten) or working fireplaces. Foul smells emanated from the moat which was clogged with rotting vegetable matter. Diseases such as typhoid and dysentery affected prisoners and guards stationed at the Fort alike. Throughout the Union and Confederacy over 56,000 prisoners died, mostly due to unsanitary conditions, overcrowding, and lack of adequate food and water.

After the war there was some local interest in modernizing Fort Mifflin to offer additional protection to Philadelphia. The Corps of Engineers constructed a large Gunpowder Magazine in 1867. Work also began on a concrete and earth battery, known today as the High Battery, to the east of the Fort, as well as a casemate for firing torpedoes into the Delaware. The Torpedo Casemate was completed in 1876; however the High Battery was never finished.

During World War I, Fort Mifflin was not garrisoned by a large cache of troops, nor did it see combat. Nevertheless, the Fort played a vital role in serving Philadelphia’s home front efforts during the conflict.

Prior to World War I, Fort Mifflin was in an utter state of disrepair. The small, outdated Fort had not held a garrison since April 1866 nor held artillery since 1904. At the time, Fort Mifflin primarily served as a tourist destination, especially popular among veterans groups and fraternal organizations. In 1915 the War Department declared Fort Mifflin a national historic monument.

However, the fort’s role changed following the outbreak of World War I when local planners developed a strategy to use older facilities such as Fort Du Pont, Fort Delaware and Fort Mifflin, for military service. To that end, the War Department provided money to modernize some of Fort Mifflin’s crumbling structures. In April 1917 District Engineer Major Mark Brooke allocated $8,000 for Fort Mifflin to repair the barracks, hospital, commandant’s house, and one magazine. Repairs concluded in August 1917, preparing Fort Mifflin for military service once again.

With Fort Mifflin restored, the important question remained of what role the small 18th century coastal fort would serve. The initial intention was to use Fort Mifflin as a storage yard to house locomotive engines and other machinery to be sent to Europe. However, the Fort’s distance from Philadelphia’s industrial center made it unfit for this task. Instead, beginning in 1918 the Fort served as part of the Fort Mifflin Naval Ammunition Depot, a large facility that stored millions of pounds of ammunition. Additionally, naval engineers laid out a small railroad, connecting Fort Mifflin to the adjacent Army Corps of Engineers Depot and the Naval Ammunition Depot.

After the war ended, the Naval Depot continued to store ammunition. However, the storage of ammunition so close to Philadelphia prompted public anxiety (one local newspaper called the Depot “an ever-present menace to the city”). As a result in 1929, the Navy redistributed the munitions, and Fort Mifflin once again entered a state of inaction.

During the Second World War, Fort Mifflin resumed the role it had served during World War I as part of the US Navy Ammunition Depot. The Army Corps of Engineers made repairs and improvements to the aging buildings. The Fort played only a small role in the defense of the Delaware River, and the site housed several anti-aircraft guns. Primary defense of the Delaware fell to Fort Miles, stationed at the mouth of the Delaware Bay.

In 1954, the federal government decommissioned Fort Mifflin, officially ending 183 years of service. The Commonwealth of Pennsylvania acquired the property and transferred ownership to the City of Philadelphia on November 14, 1962. The US Department of the Interior named Fort Mifflin a National Historic Landmark in 1970.

With the Fort’s closure, questions of management and preservation loomed over the former coastal fort. Who would maintain Fort Mifflin? Could the crumbling buildings be saved? The fort fell victim to overgrowth, deterioration, and vandalism, and it was at great risk of being lost forever.

As government officials debated the future of the Mud Island Fort, local citizens, led by Major Nicholas Biddle, Jr., sought to preserve the Fort and share its history with the public. Beginning in 1969, a local organization known as the Shackamaxon Society, later renamed the Olde Fort Mifflin Historical Society, hosted guided tours and living history programs. During the 1960s and 1970s, oversight of the Fort changed hands between local volunteers and the City. In 1986, a nonprofit organization known as Fort Mifflin on the Delaware, was founded to serve as steward of The Fort that Saved America.

Today Fort Mifflin hosts guided tours, living history programs, and a wide variety of events, including group tours, education programs, historic reenactments, scout programs, and paranormal investigations. History lives at Fort Mifflin!

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