CSS Isondiga was a wooden gunboat that served in the Confederate States Navy during the American Civil War. Designed according to Matthew Fontaine Maury's plan to produce a large number of small vessels to swamp the Union blockade, Isondiga was one of only two or three of these Maury gunboats actually completed, and the only one completed as designed. The Maury gunboats project had been almost entirely cancelled in favor of ironclad production after the Battle of Hampton Roads. Isondiga was built in Savannah, Georgia, and was transferred to the Confederate Navy in January 1863 to begin the fitting out process. At this time, she was commanded by Lieutenant Joel S. Kennard.
In late May 1863, Isondiga accompanied the ironclad CSS Atlanta in an attempt to attack the Union blockade in Wassaw Sound, but this was foiled when Atlanta ran aground. On June 17, Isondiga and the steamer CSS Resolute accompanied Atlanta in an engagement where the ironclad attacked two Union monitors and was quickly captured. At times later in 1863, Isondiga was inactivate because parts of her crew were temporarily transferred to Charleston, South Carolina. She continued service in the Savannah area in 1864. Kennard was transferred to the gunboat CSS Macon in June. In December, the city was about to fall into Union hands, and on December 20, Isondiga covered the Confederate retreat from the city over a pontoon bridge. While trying to escape herself, Isondiga ran aground and was burned by her crew on December 21 under orders from her commander, Lieutenant Hamilton Dalton.
Design
In October 1861, during the American Civil War, Confederate naval officer Matthew Fontaine Maury, who held the rank of commander, proposed that the breakaway nation's best counter to the more developed Union Navy would be to build a large fleet of small, cheap vessels in order to swamp the Union blockade. The Confederate States Congress approved construction of up to 100 vessels of a modified design in December. As approved, the design called for vessels that were long, with a beam of . The vessels were to be screw steamers armed with a rifled cannon and a Dahlgren gun. This design was known as the Maury gunboats. Contracts to build three of these vessels were awarded to the Savannah, Georgia, firm of Krenson and Hawkes. The specifications provided to the firm by the Confederate Navy placed extreme length of the hull at and extreme beam as . Each ship's keel was to measure from side to side and from top to bottom. The keelson was to be made of white oak and be across and deep. The contract allowed for the frames to be made either of white oak or yellow pine, and the frames were to be at the bottom and taper up to . The lower planks were to be either of oak or of pine, with the thickness of the upper planks to be smaller. The planks were fastened to the frames with both treenails and metal spikes, with bolts at the plank ends. The naval historian Donald L. Canney notes that this method of fastening was much more secure than that used for the larger Confederate gunboat CSS Chattahoochee, which had similar scantling dimensions.
Deck planking was to be of yellow pine, fastened down with spikes. The Maury gunboats were to be equipped with two ship's boats and the requisite davits, two anchors, a windlass, pumps, and other equipment. Isondiga had no masts and had a nominal crew strength of 60. Her draft as completed was . For much of her service, she was armed with a 6.4-inch Brooke rifle and a 9-inch Dahlgren smoothbore, but a report dated November 5, 1864, stated that she was armed with three cannon. In March 1862, the Battle of Hampton Roads convinced Confederate leadership that it would be better to build ironclads than the Maury gunboats, and funding for Maury gunboats not yet begun was removed. Canney states that only Isondiga and CSS Torch were completed of the Maury gunboats, although CSS Yadkin may also have been of the class. While Confederate naval constructor John L. Porter ordered some changes to Isondigas design, Canney notes that she was "apparently the only Maury gunboat completed as designed". In calm water, Isondiga had a top speed of about , although this was reduced by a design flaw that resulted in the propeller being partially above water. When the water was not calm, the propeller would be out of the water entirely in the troughs of waves. Her commander thought that she steered well, except that when the ship was going in reverse "the rudder had no perceptible effect on her".
Construction and service
thumb|left|Wartime map of the St. Augustine Creek area. The Savannah River is at the top of the map, with Wassaw Sound in the lower right. Causton's Bluff is circled in red in the upper left.
It is not known when Isondiga was launched, but Krenson and Hawkes received their final payment for her construction on January 17, 1863; the vessel was to have been completed over seven months earlier. At this time, the Confederate Navy took possession of the boat and began the fitting out process. Isondiga was commanded by Lieutenant Joel S. Kennard.