Hi there, I recently attended a brief presentation about the Battle of Mobile Bay (there is a cannon firing every day at the Grand Hotel in Point Clear, Alabama).
The presenter suggested that the cannon available to the Confederacy + mines effectively made it very difficult for Union ships to attack Mobile. I took his comments to mean that, at significant distance from the city, any ship traveling to the city would necessarily come within the range of cannon fire.
However, after looking at the size of the bay and doing some very preliminary research about the range of Confederate cannon, this might not be possible. At its widest, the bay is 24 miles wide. At best, CivilWarArtillery.com suggests a 10,000 yard range (and those cannon might not have been available to the Confederacy).
So, what gives? Did they mine the center of the bay, forcing ships to travel near the shore? thanks!
Not only did they have artillery at Dauphin (Fort Gaines [27 guns and 3 10-inch pieces that could fire ~5,000 yards if smoothbore and even more if rifled]) and Mobile Point (Fort Morgan [40 guns and 7 10-inch pieces with another 30 smaller guns in batteries outside of the main fortification structure]), but they also had big guns at Fort Powell on Cedar Point (6 guns with a single 10 incher). In addition to the guns, the defenses included wood pilings between Morgan and Gaines and along the coasts of Cedar Point. Mines places beyond these defenses made the actual passable waterway only 200 yards wide to enter Mobile Bay. Thats a pretty defendable space. If you include the Confederate gunboats and ironclads in the Bay and groups of batteries on the coasts, you can make a fairly strong stand. In short, the defenses made sure that craft had to move within cannon range to avoid mines and other obstacles. Check out Hearn's Mobile Bay and Mobile Campaign.
Or is the answer much simpler... Did they just have forts at Dauphin Island and... Fort Morgan?