At this section of the Delaware estuary, where the waterway narrows from a broad bay into a river, military officials in the early nineteenth century chose a strategic location for coastal defense. Fort Delaware was built on Pea Patch Island during the first half of the nineteenth century, but the rise of steam-powered naval vessels required a stronger defensive system to protect upstream ports. In the last half of the nineteenth century, Fort DuPont on the Delaware shore and Fort Mott on the New Jersey side were designed and built to reinforce Fort Delaware, creating a three-fort system that remained in use until after World War I. Finished in 1859, Fort Delaware also served as a prison for Confederate soldiers during the Civil War, and many prisoners who died there were buried at Finn’s Point National Cemetery beside the north side of Fort Mott.