It was Confederate, see this image: http://www.floridamemory.com/items/show/255295 from 1861.

This image likely refers to this event described here:https://books.google.com/books?id=OlNoBwAAQBAJ&lpg=PA152&ots=PdXQlqVk5T&dq=gulf%20steamer%20dick%20keys&pg=PA152#v=onepage&q=gulf%20steamer%20dick%20keys&f=false

An interesting tale that tells us what it was doing in 1864.
https://books.google.com/books?id=dl-mGiWVJzoC&lpg=PA360&ots=WT7fuLd9ty&dq=gulf%20steamer%20dick%20keys&pg=PA359#v=onepage&q=gulf%20steamer%20dick%20keys&f=false

In Oct 1864 it was involved in an attempt on Fort Pickens having left Fort Blakley. See: https://books.google.com/books?id=gTlAAAAAYAAJ&lpg=PA925&ots=7QfLxgoo3J&dq=gulf%20steamer%20dick%20keys&pg=PA925#v=onepage&q=gulf%20steamer%20dick%20keys&f=false

This is the simplest synopsis that indicates the Fort Pickens raid was likely her last trip, Mobile to Blakley Oct 24 1864. At least we have the name of on onboard for that trip in Lt. JM Baker CSN.
https://books.google.com/books?id=Nk9qsEI4XpAC&lpg=PA58&ots=70H_bjA5iF&dq=cs%20navy%20dick%20keys&pg=PA58#v=onepage&q=cs%20navy%20dick%20keys&f=false

JJR