The
antebellum iron industry in
Pittsburgh had thrived, fueled by access to
coal,
iron ore, and other raw materials, as well as transportation routes to get the iron to markets. In 1859, the Clinton and Soho iron furnaces introduced
coke-fired
smelting to the region. Within three years, the growing needs of the military effort during the Civil War had boosted the city's economy with increased production of iron and armaments, especially at the
Allegheny Arsenal and the
Fort Pitt Foundry. Arms manufacture included
ironclad warships and the world's first 21" heavy artillery gun. By war's end, over one-half of the
steel and more than one-third of all U.S. glass was produced in Pittsburgh. During the war, Pittsburgh's heavy industry provided significant quantities of weapons and ammunition. The Fort Pitt Foundry made mammoth iron castings for giant siege
howitzers and
mortars, among the largest guns in the world. One of the largest was a 20-inch bore
Rodman Gun, a large black powder, smoothbore, muzzle-loading coastal defense gun. The foundry produced 1,193 guns (15 percent of the total U.S. wartime artillery production) and almost 200,000 artillery projectiles. Other prominent Pittsburgh area factories included Singer, Nimick and Co. (maker of 3" Ordnance rifles) and Smith, Park and Co., which produced more than 300,000 projectiles. Pittsburgh industries collectively manufactured 10 percent of the total U.S. wartime production of artillery rounds. The Allegheny Arsenal was the primary military manufacturing facility for
U.S. Army accoutrements, as well as saddles and other cavalry equipment. In addition, the sprawling factory produced as many as 40,000 bullets and cartridges every day (more than 14 million per year), supplying between 5 and 10 percent of the Army's annual small arms ammunition requirements. A significant explosion on the afternoon of September 17, 1862 (coincidentally on the same day as the
Battle of Antietam in central
Maryland), killed 78 factory workers, mostly young women. Five
Ellet-class
rams were converted from civilian towboats at Pittsburgh. In addition, four ironclads were built from the keel up—the
USS Manayunk,
Marietta,
Sandusky, and
Umpqua. Pittsburgh's rolling mills supplied the armor for many of the ironclads that were built in
New York City and
Philadelphia for the
Union Navy. The city's 110-year run of hosting a major
stock exchange can be traced to the oil traded at Pittsburgh during the war with the creation of
Thurston's Oil Exchange on Fourth Avenue,
downtown. ==Defending Pittsburgh==