The Monitor was equipped with two impressive 11" Dahlgren smoothbores, far surpassing typical 7" - 8" cannon found on most ships. This heavy armament was possible because the low freeboard (the distance between the waterline and the deck of the ship) allowed great savings to be made in armor.
Bibliography:
- Still, William N. Jr. Monitor Builders: A Historical Study of the Principal Firms and
- Individuals Involved in the Construction of USS Monitor. Washington, DC: Department of the Interior., 1988. p.27.