Fort Mifflin - Colonial Defenses of Philadelphia

Colonial Defenses of Philadelphia

Upon foundation of Philadelphia in 1681, people recognized Mudd Island near the confluence of the Delaware River and Schuylkill River as strategically important for the defense of the settlement. William Penn, a Quaker with religious objections to military life, however, left Philadelphia undefended. Whenever European colonists established permanent settlements, fortifications in or near those settlements commonly provided protection. Quakers founded the only significant European settlements without fortification. As the Quakers rejected the military, they sought to make peace with the Native Americans in the area to avoid the need for fortifications. While other colonies suffered from conflict and warfare, Philadelphia prospered.

By the 1740s, it ranked as the richest British port in the New World. French and Spanish privateers then entered the Delaware River, threatening the city. During King George's War (1744–1748), Benjamin Franklin raised a militia, because the legislators of the city decided to take no action to defend Philadelphia "either by erecting fortifications or buildings Ships of War". He raised money to create earthwork defenses and to buy artillery. At the end of the war, commanders disbanded the militia and left derelict the defenses of the city. With renewed colonial warfare in the 1750s, people drew up plans for a fort on Mudd Island but did not implement any such plan. Only in the 1770s did the city acquire permanent fortifications.

By 1771, Philadelphia ranked as the largest British port and dockyard in North America. Locals then rose in protest against British economic policies and imports. In response to complaints by the Secretary of State for the Colonies, Philadelphia Governor John Penn asked General Thomas Gage to send someone capable of designing defenses for the city. He intended a fort on Mudd Island to help to regulate traffic entering and exiting the port. Gage assigned Engineering Captain John Montresor to the task. Montresor presented six designs to Penn and the Board of Commissioners; the board proposed constructing a fort on Mud Island (also known as Deep Water Island).

The commissioners reviewed the plans, found all too expensive, and insisted on economy despite protestations of Montresor about budget. Montresor stated that his preferred plan cost about £40,000 and that he intended to mount "32 pieces of cannon, 4 mortars and 4 royal howitzers ... which at 6 men each make 240 men required, 160 musketry, in all 400 garrison." The colonial General Assembly passed a bill releasing £15,000 for the construction of the fort and the purchase of Mud Island from Joseph Galloway, the Speaker of the House. The board instructed Montresor to begin construction but failed to provide him with the funds that he considered necessary to do so properly. The rooms in the farthest interior of "casemate #11" probably date from the original construction in 1771. On 4 June 1772, Montresor left the head workman in charge of the construction project and returned to New York disgruntled. The project floundered onward for about a year, when it stopped for lack of guidance and funding. The crews completed only the south walls, built in stone.

• John Montresor's survey of Mud Island, 1771

• Montresor's Design #1, proposed fort on Mud Island

• Montresor's instructions for driving piles at Mud Island, PA