Sorry to get into this a little late. Thanks to Uncle Jaque for some good info. About the four string banjo. Folks like to think that it came before the five stringer. Not so, that is the tenor banjo and it's longer necked cousin, the plectrum. The tenor came about in the 20's when folks were hunting around for a string instrument loud enough to hold up to the brass in jazz bands. Proof of the five string during the Civil War? Look at almost any photo of a crew on a war ship of that time. There will be a banjo player there with the five stringer.

Rex