According to one account written at the time (I have to find the source, I just read this!) there would not have been any troops stationed at the Forts had it not been for the trouble in Mexico. With European powers threatening to land forces in Mexico, the United States stationed the bulk of the US fleet off of Vera Cruz and placed troops in certain forts along the coast of the United States in 59-60. Charleston was one of these post that was manned, normally there would only have been a caretaker.

Also the commander of the Federal forces at Charleston was given the option to move his command in 1860 to North Carolina when the Yellow fever came, but it never did that year.

David