USS Marmora, a 207-ton stern-wheel "tinclad" river gunboat, was built in 1862 at Monongahela, Pennsylvania, as the civilian steamer Marmora Number 2. Purchased by the Navy and converted to a gunboat, she was commissioned October 1862. Marmora was soon sent to join the Federal forces campaigning against the Confederate fortress at Vicksburg, Mississipi. During the rest of 1862, she took part in mine clearance and other operations in the Yazoo River. In January 1863, Marmora went up the White River to help capture Fort Hindman, Arkansas, and subsequently was active on the Yazoo, White and Little Red Rivers. Decommissioned in July 1865, following the end of the Civil War, USS Marmora was sold the next month.