Commonwealth was a large sidewheel steamboat built in 1854–55 for passenger service on Long Island Sound. The most celebrated Sound steamer of her day, Commonwealth was especially noted for the elegance and comfort of her passenger accommodations, which included gas lighting, steam heating, and an "enchantingly beautiful" domed roof in her upper saloon. Her stability of motion led her captain to describe Commonwealth as the finest rough weather steamboat ever built in the United States. Commonwealth would spend her entire career on Long Island Sound routes, first from New York to Allyn's Point, Connecticut under the management of the Norwich and New London Steamboat Company, and later to Stonington and Groton with the New Jersey Steam Navigation and the Merchants' Steamship companies. During the American Civil War, she was part of the transport network that moved northern state Union regiments to the battlefront. Commonwealths end came prematurely when she was destroyed by a dockyard fire at Groton in December 1865. Construction and design Commonwealth was built by Lawrence & Foulks at Williamsburg, New York for the Norwich and New London Steamboat Company, which ran a steamboat line between New York City and Connecticut. About 18 months in construction, she was completed in March 1855. Dimensions and hull design Commonwealth had an overall length of 330 feet (100 metres), with a length on deck of 316 feet and 300 feet along the load line, making her one of the largest steamboats on the sound. She had a beam of 42 feet—77 feet over the guards—a hold depth of 13 feet 6 inches and a gross register tonnage of 1,732 tons. For a vessel of her size and tonnage, she drew a surprisingly light draft of scarcely more than 8 feet in running trim. Commonwealths hull design was considered to be exceptional—"worthy of examination by all professional architects." The hull was flat-bottomed with an external keel, and the bow sharply angled. The midship section was duplicated for 56 feet fore and aft—an original feature in steamboat design—and the broad beam was considered an aid to stability. Like all large American wooden-hulled steamboats of the era, the hull was supported by heavy hog frames and iron tie-rods suspended from king posts to prevent excessive hogging, but in Commonwealths case it was also strengthened with diagonal iron braces "after the manner of fastening the first-class sea-going steamships", and constructed throughout "with great reference to