On April 29, 1861
Secretary of the Navy Gideon Welles received correspondence from James Eads concerning the viability of converting
Submarine No. 7 into a riverine warship for the U.S. military.
Submarine No. 7 was a snagboat built by the
US Navy that had been purchased by Eads' Missouri Wrecking Company and modified to raise sunken steamboats on the
Mississippi River. Both hulls of
Submarine No. 7 were divided into 7 watertight compartments and Eads argued that the vessel could suffer up to 20 penetrating shot into 4 of these compartments and still stay afloat. (Other sources state she was built with 40 watertight compartments.) He argued that the vessel would be able to support a strong battery of 32-pounder cannons. His initial proposal called converting the vessel into a
Cotton-clad gunboat for a cost of $3,000 in cotton. His letter also described a plan to convert two other, smaller vessels and to create a
naval base at
Cairo, Illinois. Lacking the resources to undertake the project, Welles forwarded Eads's letter to the
Secretary of War Simon Cameron. Cameron was impressed by the proposal and forwarded it to
General George McClellan to implement the construction of the base. Instead of the cotton-clad boat however, the US Army wanted a fleet of new ships; this became the
City-class ironclad fleet. Eads earned several additional contracts after impressing the authorities with his abilities during the construction of the
City-class. One of the vessels involved was
Submarine No. 7. Eads widened the lower deck of
Submarine No. 7 into a gun deck then added a second tier of accommodations. The large size of the finished vessel and this additional space led to the vessel being well suited to a flagship role.
Commander William D. Porter complained that the finished vessel was too slow, and history has recorded that Eads replied that she was still fast enough to fight in. Now as the
Benton, she would serve as a flagship for most of the war. == Armament ==