Yeah, USS Ozark in 1863 had *four* shafts
USS Dictator in 1863 was 2 shaft
The 1854 Stevens Battery design had twin shafts, but while she was laid down she was never completed.
Ohhh.... I found one! USRC Naugatuck was built in 1844, in service in 1862 as a coastal ironclad. Twin screws...