I am aware that they are not properly seagoing craft, that they are very slow, work heavily against a current or tide, are liable to founder, and the like, but . . .” Thus did Massachusetts Governor John A. Andrew beg U.S. Secretary of the Navy Gideon Welles in a 4 May 1863 letter—for a second time—to have one of the six new monitors, then under construction in Boston, assigned to protect its harbor.
The ships were part of a 20-ship class of very shallow draft ironclads designed for the waters of Southern rivers and estuaries and the Western waterways. They were fostered by Assistant Secretary of the Navy Gustavus Vasa Fox, who believed a monitor with a six-foot draft was the answer to combating Confederates in their own domain. In August 1862, Fox asked John Ericsson, the prototype Monitor’s designer, to take on the project. Ericsson responded in October with estimates and sketches for a single-turret, two-gun monitor with a 221-foot-long, 41-foot beam hull.
The Navy’s chief engineer, Alban C. Stimers, was assigned to fill in the details of Ericsson’s work. Ericsson believed Stimers would work within the parameters of his sketches and estimates, and Fox thought the chief engineer would consult with Ericsson about changes. Neither happened.
When the Swedish inventor saw the final plans on 24 February 1863, he “repudiat[ed] all responsibility” for the ship. Among the many changes Stimers introduced were to the boilers and propellers and for a complete redesign of the ship’s armor, such that “the sides are not shot proof.” Worse was the addition of water tanks, which would allow the ship to lower herself even farther into the water (thus negating its six-foot draft) and pumps to expel the water to raise the ship should she run aground (which would not have occurred had she retained her six-foot draft). The tanks, two feet wide and six feet deep, completely surrounded the ship’s perimeter. Two steam-driven water pumps were added as well as all the plumbing and actuating equipment required. This added not only to the complexity of the ship’s operation, but also to her weight.
Ericsson was livid. His original premises of simple construction and invulnerability had been lost. The added tanks only changed the draft by six inches, the new boilers weakened support for the overhead deck and armor, and the propeller change increased the beam of the stern, making the ship less maneuverable.
Despite these objections and others, the Navy proceeded to release Stimers’ design for bids for 20 ships with delivery by early 1864. The ships sat on the ways for months at yards and were beset by numerous design changes emanating from Stimers’ hand. When the first, the Chimo, was launched at South Boston on 5 May 1864, her freeboard—without turret, guns, coal, ammunition, and stores—was just 3 inches, not the 15 inches of her design calculations. Navy Constructor W. L. Hanscom, who was inspecting the ship, was asked about the tanking system to “sink the vessel down.” With no little irony, he responded, that with these ships, “It was entirely unnecessary.”
Stimers, however, remained optimistic that the ships could be fixed, and Fox, unaware of the severity of the situation, believed him. But in early June, Stimers told Fox that Ericsson wanted the monitors to fail because the inventor believed Stimers was a “formidable rival” and he would bring “grief” to Fox because the Assistant Secretary was an “utter” incompetent. Welles and Fox had had enough and replaced Stimers with William W. W. Wood and suspended work on the remaining ships.
A committee was formed to find a way to make the ships serviceable—or at least able to float. Its members chose two approaches. The first five ships—the Casco, Naubuc, Napa, Chimo, and Modoc—completed without turrets and each armed with a spar torpedo, were designated as torpedo vessels. The first three also each mounted one XI-inch Dahlgren gun on the foredeck, while the Chimo added a 150-pounder. The water-pumping system was abandoned as well as the armored funnel. The result was a slow torpedo ship—capable of barely five knots—with no protection for her gun crew.
The remaining 15 ships each had their upper decks raised by 22 inches, with the work affecting all the structural components within the hull. Their sterns were modified to aid propeller efficiency, and stiffening plates were added to the frames. The Etlah, completed to this design, drew eight feet of water with a one-foot freeboard.
The Casco class, originally contracted at an average of $400,000 ($6.5 million in 2020 dollars), cost the government between $513,000 and $648,000 ($8.4 million to $10.6 million). But what the Navy received in return were barely functional ships. Only four—the Chimo, Casco, Tunxis, and Naubuc—were commissioned before the end of the Civil War, and just four others were commissioned after. The remaining dozen were placed into ordinary once they were launched, and all were sold for scrap in 1874 and 1875.