One of the features of Fort Cumberland was the system of earthworks which today are known as the Tunnels. They are all that visibly remains of the fort.
Originally, these served three purposes. Beneath the storehouses in the fort, underground chambers were dug for the purpose of keeping perishable food fresh for as long as possible. The 5000 people at the fort ate 15000 meals a day! As well, gunpowder had to be stored with great care, and some of the chambers were lined with stone to serve as powder magazines. One still exists beneath the Church. Finally, the fort was made of wood, and thus highly vulnerable to attack. So along the banks of the Potomac and Will’s Creek to the east and south, and surrounding the fort at a distance of ¼ mile to the north and west were out defense works. These were accessed from the fort by trenches that extended out from beneath the fort’s walls.
100 years later, the same trench that once gave British soldiers a way to reach their defenses along Will’s Creek in safety became the way escaping slaves got up under the Church to the safety of the Underground Railroad station.