The American Civil War saw a wide array of new forts spring up across America, while many older ones were called into service. There's Fort Sumter, where it all started, and Fort Gaines, which was the site of a key battle. Others had more low-key but no less vital roles to play in the conflict, and they're all fascinating examples of historic military architecture.

Many of these structures are now open to the public. Click through this gallery to see the amazing forts that shaped the Civil War….