USS Cairo USS " Cairo " was a City class ironclad gunboat constructed for the Union Navy by James B . Eads during the American Civil War . She was the first vessel of the City class ironclad s , also called the " Cairo " class . " Cairo " was the first ship sunk by a naval mine , on 12 December 1862 in the Yazoo River . Service in the American Civil War . " Cairo " was built in 1861 by James Eads and Co . , Mound City , Illinois , under contract to the United States Department of War . She was commissioned as part of the Union Army ' s Western Gunboat Flotilla , U . S . Navy Lieutenant James M . Prichett in command . " Cairo " served with the Army ' s Western Gunboat Flotilla , commanded by Flag Officer Andrew Hull Foote , on the Mississippi and Ohio Rivers and their tributaries until transferred to the Navy 1 October 1862 with the other river gunboats . Active in the occupation of Clarksville , Tennessee , 17 February 1862 , and of Nashville , Tennessee , 25 February , " Cairo " stood down the river 12 April escorting mortar boat s to begin the lengthy operations against Fort Pillow . An engagement with Confederate gunboats at Plum Point Bend on 11 May marked a series of blockading and bombardment activities which culminated in the abandonment of the Fort by its defenders on 4 June . Two days later , 6 June 1862 , " Cairo " joined in the triumph of seven Union ships and a tug over eight Confederate gunboats off Memphis , Tennessee , an action in which five of the opposing gunboats were sunk or run ashore , two seriously damaged , and only one managed to escape . That night Union forces occupied the city . " Cairo " returned to patrol on the Mississippi until 21 November when she joined the Yazoo Expedition . On 12 December 1862 , while clearing mines from the river preparatory to the attack on Haines Bluff , Mississippi , " Cairo " struck a torpedo detonated by volunteers hidden behind the river bank and sank in 12 minutes ; there were no casualties . Armament . Like many of the Mississippi theatre ironclads , " Cairo " had her armament changed over the life of the vessel . To expedite the entrance of " Cairo " into service , she and the other " City " - class ships were fitted with whatever weapons were available ; then had their weapons upgraded as new pieces became available . Though the Dahlgren smoothbore cannons were fairly modern most of the other original armaments were antiquated ; such as the 32 - pounders , or modified ; such as the 42 - pounder " rifles " which were in fact , old smoothbores that had been gouged out to give them rifling . These 42 - pounder weapons were of particular concern to military commanders because they were structurally weaker and more prone to exploding than purpose - built rifled cannons . Additionally , the close confines of riverine combat greatly increased the threat of boarding parties . The 12 - pounder howitzer was equipped to address that concern and was not used in regular combat . The USS Cairo has erroneously been stated that she was sunk by an electrically detonated torpedo . The actual detonator used was a friction primer commonly used in setting off the powder charge in cannon . Discovery of the Wreck . Over the years the gunboat was forgotten and her watery grave was slowly covered by a shroud of silt and sand . Impacted in mud , " Cairo " became a time capsule in which her priceless artifacts were preserved . Her whereabouts became a matter of speculation as members of the crew had died and local residents were unsure of the location . The location at which the ship rested was forgotten over time , and was covered by the moving river . The presence of mud and silt caused the ship to be preserved against corrosion and biological degradation . Studying Civil War maps , Edwin C . Bearss of Vicksburg National Military Park set out to search for the lost ship using metal detectors . With the assistance of Don Jacks and Warren Grabau , it was found in 1956 . In 1960 , numerous artefacts were recovered from the ship , including the pilothouse , and an 8 - inch cannon , being preserved by the Yazoo River mud . With support from the State of Mississippi and local authorities , the gunboat was salvaged from the bottom of the river . Salvage and museum . Hopes of lifting the ironclad and her cargo of artifacts intact were crushed in October 1964 when the three inch cables being used to lift the " Cairo " cut deeply into its wooden hull . It then became a question of saving as much of the vessel as possible . A decision was made to cut the " Cairo " into three sections . By the end of December the battered remains were put on barges and towed to Vicksburg , Mississippi . In the summer of 1965 the barges carrying the " Cairo " were towed to Ingalls Shipyard on the Gulf Coast in Pascagoula , Mississippi . There the armor was removed , cleaned and stored . The two engines were taken apart , cleaned and reassembled . Sections of the hull were braced internally and a sprinkler system was operated continually to keep the white oak structural timbers from warping and checking . On 3 September 1971 , the " Cairo " was listed on the National Register of Historic Places . In 1972 , the United States Congress enacted legislation authorising the National Park Service to accept title to " Cairo " and restore the gunboat for display in Vicksburg National Military Park . Delays in funding the project halted progress until June 1977 , when the vessel was transported to the park and partially reconstructed on a concrete foundation near the Vicksburg National Cemetery . A shelter to cover the vessel was completed in October 1980 , with the museum opening in November . The original space - frame shelter has recently been replaced by a tension - fabric system to provide better cover . The recovery of artifacts from " Cairo " revealed a treasure trove of weapons , ammmunitions , naval stores , and personal gear of the sailors who served on board . The gunboat and its artifacts can now be seen along the tour road at the USS " Cairo " Museum . These even include a sailor ' s rope knife in very good condition , as reported in " Knives and their Values , 4th edition " by Bernard Levine . Since salvage , the " USS Cairo " has suffered degradation due to exposure to the elements , bird droppings , and vandalism . Perhaps with the new quarter that will be released in 2011 a fund could be established to enclose the best - preserved Civil War ironclad . There are only three surviving Civil War - era ironclads in existence , CSS Neuse , USS Cairo , and CSS Jackson ; soon " Cairo " will be the only one outdoors in the brutal Southern climate . References . " This article includes information from the National Park Service and is in the public domain . "