Philadelphia in Philadelphia County, Pennsylvania — The American Northeast (Mid-Atlantic)
Fort Miﬄin (Mud Fort) on Mud Island
Report from the Fort (during construction)
25 September 1794 . Pierre Charles L’Enfant, Engineer to Henry Knox, Secretary of War
A place destitute of every comfort for the hands [workmen]; lay open to all accidents of the season [and was] uncommonly bad in the months of June, July and August, when extraordinary freshes [floods] and storms greatly injured the work and caused an increase of labor which could not have been foreseen nor avoided, having had successively to repair the extensive bank round the Island, to build new sluices, open new drains, and dig over and over all ditches, without which the whole Island must have been overflowed; the whole work upset, and the laboring hands with the garrison, reduced to the most unhappy situation.
Report from the Fort
21 January 1802 . Major J.J. Ulrich Rivardi, Commander of Fort Mifflin
to Jonathan Williams, Inspector of Fortifications, West Point
Mud Island is about one mile in circumference 740 yards from north to south and about 300 from east to west, forming a kind of irregular oval. The whole would be overflowed at high water, if it was not protected all round by a solid bank about six feet high which admits through two sluices (one to the east the other to the west) water enough to clean in a few hours the ditches
Mud Island was created from silting caused by the flow of the Schuylkill River into the Delaware River. It has always been low, marshy, and likely to flood. When the site was selected for a fortification to protect Philadelphia in 1771, it was separated from the mainland by a channel about 500 yards wide and buffered to the south by a larger land mass, Hog Island. Access to Mud Island by road included a boat to cross
Because Mud Island sits below mean high water level, dikes, ditches, and protection of the river banks have been requirements to keep the island drained and dry. These factors have affected construction and maintenance of the fortification throughout its existence. The dampness, wind, mosquitoes, poor drinking water, and isolation influenced all who were stationed at the fort.
The moat around the fort served not only as a system of drainage and water supply, but also as a defense against sieges or mining by the enemy. The pre-Revolutionary moat, called a “wet ditch,” was narrow and only went around three sides. In reconstructing the fort after the Revolution, the moat was dug to encircle the new fort walls and widened to thirty feet. Mud dug from the ditch was always recycled into the ramparts or river banks to fill in holes made by the river, muskrats or other wildlife. The river water was the only source of drinking water, and a clean, free-flowing moat was critical to the health
Because of the low and wet land, standard European engineering techniques for construction in wet soil were used by John Montrésor for the first stone walls built in 1772. The same practice was continued during the reconstruction of the fort in 1778, and furthered by Pierre Charles L’Enfant for the completion of the new walls from 1791-98. Piles (actually trees) were dropped into the moat and an interlaced platform of planks were fastened to the ends. Constant submersion of the wood in water kept it from rotting. Stones for the walls was laid on top of the wooden platforms.
The stone walls along the east and south sides stem from the 1772 pre-Revolutionary construction designed by Montrésor. They were essentially free-standing with buttresses for support and were the only permanent walls at that time.
After the Revolution the early stone wall was rebuilt, and brick was used to complete the fort as an enclosed, irregular star-shaped design with two bastions. Earthen ramparts and brick casemates or bombproof vaults were added inside
Erected by Fort Mifflin Historic Site.
Location. 39° 52.553′ N, 75° 12.761′ W. Marker is in Philadelphia, Pennsylvania, in Philadelphia County. Marker is on W Fort Mifflin Road, on the right when traveling east. Click for map. Marker is along the walking tour of Fort Mifflin. Marker is in this post office area: Philadelphia PA 19153, United States of America.
Other nearby markers. At least 8 other markers are within walking distance of this marker. Soldiers’ Barracks (within shouting distance of this marker); Quartermaster’s Store (within shouting distance of this marker); From Marsh to Solid Ground (within shouting distance of this marker); Officers’ Quarters (within shouting distance of this marker); Casemates or Bombproofs (within shouting distance of this marker); Arsenal (within shouting distance of this marker); Artillery (within shouting distance of this marker); Fort Mifflin (within shouting distance of this marker). Click for a list of all markers in Philadelphia.
More about this marker. The marker contains a number of maps and illustrations of Fort Mifflin. The bottom of the marker shows Fort
Related markers. Click here for a list of markers that are related to this marker. This series of markers follow the walking tour of Fort Mifflin.
Also see . . .
1. The Fort that saved America. The Official Website of Fort Mifflin on the Delaware. (Submitted on October 13, 2008, by Bill Coughlin of North Arlington, New Jersey.)
2. The Siege of Fort Mifflin. The Philadelphia Campaign, 1777. (Submitted on October 13, 2008, by Bill Coughlin of North Arlington, New Jersey.)
3. Fort Mifflin Groundplan. Layout of Fort Mifflin, the Fort that saved America. (Submitted on October 13, 2008, by Bill Coughlin of North Arlington, New Jersey.)
Categories. • Forts, Castles • Notable Places • War, US Revolutionary •
Credits. This page originally submitted on , by Bill Coughlin of North Arlington, New Jersey. This page has been viewed 2,326 times since then and 31 times this year. Photos: 1, 2, 3, 4, 5, 6. submitted on , by Bill Coughlin of North Arlington, New Jersey. This page was last revised on June 16, 2016.