Born in Brooklyn, New York, he joined the Union Navy as a "cabin boy" at age 15 during the American Civil War, during which he was wounded in action.

On June 7, 1889, he founded the Carpenter Steel Company of Reading, Pennsylvania, becoming its general manager.

[7] In May 1861, at the start of the American Civil War, the 15-year-old Carpenter enlisted as a "cabin boy"[8] and was assigned to USS Santee, a recently commissioned 44-gun wooden-hulled three-mast frigate under the command of Captain Henry Eagle.

Santee arrived in the Gulf of Mexico in July, headed for Galveston, Texas, for Union blockade duty.

He was selected for a night-time cutting out operation that was intended to capture and burn the Confederate armed steamer General Rusk.

After evaluation he was appointed on February 21, 1862, as master's mate to the steamer USS R. R. Cuyler[10] and took part in the capture of several enemy vessels.

[5] On June 20, 1862, R. R. Cuyler's captain reported that Carpenter's good work "justifies the suggestion that he should endeavor to obtain admission to the U.S.

Carpenter left R. R. Cuyler on September 22, 1862, and was assigned to USS Constitution until he was discharged as a sailor on November 28, 1862.

[5] The United States Naval Academy (USNA) had been relocated to Fort Adams in Newport, Rhode Island, for the duration of the Civil War.

[5][9] During 1863–1865 Carpenter's academic work was generally good and he excelled in the sciences, but later he accumulated many demerits, which brought him restrictions and extra duties.

[12] Carpenter was one of the cadets who sailed on Santee on August 2, 1865, to return to the USNA at Annapolis, Maryland, where the strict pre-war discipline and decorum of spit and polish was re-instituted.

49, dated 23 Nov 1865" from Rear Admiral David Dixon Porter "regarding the resignation of James Henry Carpenter, age 19, member of the 3rd class" indicates a deterioration in attitude and commitment.

While finishing school, he met Theodora Anna Silvera (Siloena), born about September 2, 1846, in New Jersey.

Shortly after 1880[15] the family moved to Hartford, Connecticut, where Theodora died on February 2, 1883, from complications during childbirth.

[5] Carpenter then went to seek engineering work in Chicago, where he met Georgian Clara Smith (born June 1865 in Canada; died August 21, 1930) of Saint Paul, Minnesota.

[1] Within a short time, 3,000 tons of steel had been produced and the company was receiving orders that exceeded the capacity of the mill.

Photographs of the era depict employees receiving medical care at company sponsored health clinics, clean dormitory rooms provided to workers, employees engaged in spirited games of baseball on a Carpenter Steel-maintained field at lunch time, and happy workers participating in a local parade.

[17]Carpenter bought property and built an Italianate house at 606, North Fifth Street, Reading, which he called Swanona (not Swannanoa).

[5] Carpenter filed an application on March 14, 1895, with the title "Apparatus for treating Ingots of Steel", but there was a further delay before the patent was finally awarded on July 3, 1900.

In November 1896, the Navy informed Congress that Carpenter's projectiles had tested successfully, calling them "the first made that would pierce improved armor plate".

Increased debts, business costs, employee benefits and other economic factors were the main part of the problem.

[18][22] Carpenter special steel was used in the early airplanes of the Wright brothers and in Glenn Curtiss aircraft and continues to be used in many types of high-performance craft.