The Hessian Powder Magazine, also known as the Hessian Guardhouse Museum, is an historic guardhouse and gunpowder magazine which is located on the grounds of the Carlisle Barracks in Carlisle, Cumberland County, Pennsylvania.

Built in 1777, the Hessian Powder Magazine is a stone walled structure, which is lined with interior brick.

It also has a vaulted stone roof, which is covered by timbers and tin, creating a gable form.

[2] Tradition says that Hessian prisoners of war, who were captured during the Battle of Trenton were sent to Carlisle, and used to build this guard house, which was originally a magazine.

[2] Afterwards, it was used as a quartermaster and medical supply storehouse, filmstrip laboratory, message center, and U.S. post office.