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.

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,[7] but in Commonwealth's 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 strength and safety.

"[5] This assessment would be borne out in practice: Commonwealth's longstanding captain, Jerome W. Williams, would later describe the vessel as "the finest boat for rough water ever built" in the United States.

[8] Commonwealth was powered by a 1,200 horsepower,[2][4] 19 rpm single cylinder vertical beam steam engine, with 76-inch bore, 12-foot stroke and Stevens cut-off set at 7 feet, built by the Morgan Iron Works of New York.

It is painted with exquisite taste a pure white, for any attempt at ornamentation would mar its graceful and beautiful proportions; and gilding and gingerbread work are used with a sparing and chastened hand in all parts of this splendid vessel.

[2]The saloon deck also featured an after cabin fitted with thirty large sofas, allowing passengers to "sit and enjoy the magnificent prospect of the evening passage on the Sound with comfort.

The staterooms were large, well-ventilated, and designed with "Oriental elegance", incorporating materials such as satin damask, moquette, lace, velvet tapestry, and rosewood furniture.

The servants designed their own livery: black pants, white vests and jackets, and blue velvet caps with silver trimming and the letters "C. W." in beadwork at the front.

Their choice of skipper for the vessel was Captain Jerome W. Williams, a seaman with almost 25 years of navigational experience on Long Island Sound, and known for his "cool, clear head and good judgement".

[16][17][18] For Commonwealth's debut, the Railroad itself introduced a number of "splendid new sixteen wheel" railway carriages as a means of increasing the attraction of the service.

"[22][23] In June 1857, a woman reportedly fell overboard from Commonwealth at the New London wharf, and could not be extricated from the water for half an hour, during which time the buoyancy of her hoop dress was said to have saved her from drowning.

[27][28] With the outbreak of the American Civil War in April 1861, the U.S. government requisitioned hundreds of steamboats and steamships to serve as transports, gunboats and blockade ships.

In this role she would still however contribute to the war effort, as part of the transport network that brought newly recruited regiments and their supplies from the northeastern United States to the battlefront.

As early as May 1861, Commonwealth was engaged in transporting troops from Connecticut to New Jersey, when elements of the 40th "Mozart" Regiment, New York Volunteers, embarked at Stonington on the 31st.

[34][35] Commonwealth was capable of accommodating an entire 1,000-man regiment plus additional passengers on a single voyage, but conditions in such circumstances were not always ideal—the 11th Rhode Island, for example, complained of a shortage of suitable sleeping arrangements.

[35] Regiments transported on Commonwealth in late 1862 were treated to "fine view[s]" of the mammoth British steamship Great Eastern,[33][35] then laid up in New York Harbor for extended repairs.

[30][32][33][35] While the meal was greatly appreciated, some soldiers are said to have left the city with fonder memories still of the passionate embraces of the local females, who lined the streets to bid them farewell on their departure.

[1][42][43][44] Fortunately, most of Commonwealth's passengers had already disembarked and departed by train, but a young medical student named J. Dickson Ripley, a nephew of Connecticut Governor William A. Buckingham, could not be aroused despite repeated poundings on his cabin door and was presumed to have suffocated from smoke inhalation in his sleep.

[43][45] In addition to the loss of Commonwealth, the entire depot at Groton was destroyed,[1][42][43][44] so thoroughly that the Railroad was forced to move its terminus back to its former location of Stonington for a time.

William Foulks, partner in the shipbuilding firm that constructed Commonwealth, won the gold medal in the naval architecture division of the American Institute of New York's 27th Annual Fair in 1855 for a model of the vessel.

[46] The American jewelry firm Tiffany & Co. won the bronze medal for silverware at the Paris Exposition of 1867 for a display which included an "exquisite" silver model music box of Commonwealth.

[47][48] This model was made by John Dean Benton, a Tiffany silversmith, and it played ten airs of the day[49] including ‘Nellie Bligh’ and ‘By Banks and Braes of Bonnie Doon.’[50] An 1864 edition of Scientific American describes the model in detail: In its construction seventy-three ounces of gold were used, and two hundred and fifty-two ounces of silver, and skilled mechanics have been employed upon the work for six months, at an aggregate cost of six thousand five hundred dollars.

Not only the smoke-stacks, flag-staffs and deck machinery are carefully copied, but the panels of the saloons, the window shades, and all the intricate and delicate handiwork which appears on the steamer, are accurately represented.