Fort Popham was originally designed to mount 42 heavy guns, a mix of 10-inch and 15-inch Rodman guns, but construction was halted in 1869 with only two of the planned three tiers completed. In the late 19th century, Fort Popham's armament consisted of 36 Rodman guns and some 300-pounder (10-inch) and smaller Parrott rifles. One of the Rodman guns was donated to the town of Bowdoinham to remember its soldiers who died in the Civil War. The cannon is still there. A 100-pounder (6.4-inch) Parrott rifle sits near the fort grounds; it was listed as being at the fort in 1903. The back side of Fort Popham was built with a low moated curtain containing a central gate and 20 musket ports.