although this was reduced to when going upstream. McDonald used Marmora several times, including transporting Union Army troops down the Kanawha River in August. At that time she was also in use for transporting passengers and freight, running between Pittsburgh, Pennsylvania, and Cincinnati, Ohio. With the American Civil War ongoing, the Union Navy was seeking to increase the number of ships it operated, and the navy purchased Marmora for military use on September 17, at a cost of $21,000, () from C. Brennan, William Nelson, and James McDonnell. Marmora was converted into a tinclad warship. The process of converting a civilian steamer into a tinclad involved arming the ships, installing a wooden casemate that was at least partially covered with thin iron armor, replacing the pilothouse with a new armored one, reinforcing decks and internal beams, and generally removing the texas. Tinclad warships were used to patrol rivers, protect and escort other vessels, and sometimes act as naval support for military actions. Marmora was assigned the identification number 2; these numbers were painted onto the pilothouses of the tinclads beginning in June 1863. She was commissioned into the Union Navy on October 21, at Carondelet, St. Louis. Over the course of her military service, her armament varied. Initially, Marmora was armed with two 12-pounder rifled cannons and two 24-pounder guns. In June 1864, four 24-pounder guns were added to her armament, which consisted of eight 24-pounder guns as of the following December. As of March 31, 1865, she was reported to have been armed with two 12-pounder guns and six 14-pounders. Along with USS Signal, Marmora was one of the first purpose-converted tinclads in the Union Navy. Service history Vicksburg campaign Marmora left Carondelet for Cairo, Illinois on October 22, under the command of Acting Volunteer Lieutenant Robert Getty. In November, Union Army Major Generals Ulysses S. Grant and William T. Sherman, along with Acting Rear Admiral David Dixon Porter, decided that the Union Navy would operate against Confederate forces along the Yazoo River, in junction with the Vicksburg campaign. Porter's command was known as the Mississippi Squadron. On November 21, Captain Henry A. Walke received orders to move with a naval force from Helena, Arkansas, to the mouth of the Yazoo. Marmora was at Cairo at this time, and was ordered to join Walke. The vessel reached Helena on November 24, and left for the mouth of the Yazoo