Steam sloop USS Pocahontas capturing a blockade runner off Mobile Bay (source; Library of Congress archives):
In a prior post (18 February 2012) I commented on the importance of the Port of Mobile, Alabama to the Confederacy. While Mobile had a number of major advantages, primarily its rail connections to other parts of the Confederacy, it was a difficult endeavor to run the blockade into Mobile Bay, for a number of reasons.
There were three entrances into Mobile Bay: the first, a westward entrance known as Pelican Channel. Shallow depths in this entrance generally precluded its use, The second entrance was the “Swash Channel”. This was the entrance most used by runners because even though it was shallow (12 feet), it was difficult for blockaders to move “off station” to cut out runners through this entrance, plus Confederate shore batteries could cover this entrance and keep blockaders off at a safer distance. The third entrance was the Main Channel, but this was the easiest for the blockading fleet to cover. Despite these difficulties, there was a huge amount of blockade running into and out of Mobile, especially after New Orleans was captured by Union forces in April 1862. Most of the traffic came to and from Cuba, which was the main waypoint for blockade runners in the Gulf of Mexico.
Running the blockade into Mobile really came into its own after the Confederate Navy began to contract for and acquire pure “blockade runner” ships designed for this purpose (see post by Gordon on 24 July 2010). These shallow draft, fast, “stealth” ships (low profile, painted grey or black) were able to slip in and out of the port a number of times undetected, mostly at night. The major runners operating out of Mobile were the CSS Denbigh, the Donegal, and the Mary. All were British-built side-wheel steamers, specifically designed to run the blockade.
Blockaders off Mobile Bay (source; Naval History and Heritage Command photo archive):