The Fortress is a military building in American Conquest and American Conquest: Fight Back. It is needed to produce more advanced units like Fusiliers, 18th century officers, drummers, standard bearers, field artillery and cavalry.

Like the Fort and the Blockhouse II, the Fortress can shoot with cannons on enemies once there are units or peasants inside. This can be risky at times, since they can also hit and set ablaze your own or allied buildings if they are in the way.

Some Native Americans like the Maya, the Incas or the Aztecs also have fortresses, but they have no cannons to their defence.