Pittsburgh in the American Civil War Pittsburgh , Pennsylvania was a thriving and important city during the American Civil War , and provided a significant source of personnel , war materiel , armament , ammunition , and supplies to the Union Army . Situated at the confluence of the Monongahela , Allegheny and Ohio rivers , Pittsburgh was an important transportation hub for both riverine and rail transport , as well as overland via its system of roads . Production of materiel . 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 howitzer s 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 , concurrent with the Battle of Antietam in central Maryland ) , killed 78 factory workers , mostly young women . Five " Ellet " - class ram s 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 . Both the Confederate military led Morgan ' s Raid from the west and Jones - Imboden Raid from the south came within a days march of the city before being captured or retreating . Concerned that the Confederate Army might target Pittsburgh for invasion , the U . S . War Department established the Department of the Monongahela to provide a formal Federal military presence in Western Pennsylvania during the Gettysburg Campaign , with departmental headquarters in Pittsburgh . The Army dispatched Maj . Gen . William T . H . Brooks to organize the defenses of Pittsburgh . Brooks authorized the construction of several miles of earthwork s and a series of small forts to control access to the city . He suspended liquor sales , and put the citizenry to work digging trenches and erecting forts . Bars and saloons were asked to close but many refused . Among these bastions was Fort Robert Smalls , a redoubt built by free blacks on McGuire ' s Hill at the mouth of Becks Run in Arlington Heights . Another of these emergency fortifications was the circular earthwork known as Fort Laughlin , constructed by the employees of Jones and Laughlin Steel on " Ormsby ' s Hill " , now part of Arlington Park on Arlington Avenue . It was also known as " Fort McKinley " or " Fort Ormsby " . Concurrent with Fort Laughlin , Jones and Laughlin Steel employees constructed Fort Jones , named for the mill ' s co - owner , Benjamin Franklin Jones . Fort Jones occupied the top of a hill in Mount Oliver . It was sometimes known as " Fort Jackson " , in honor of Brig . Gen . Conrad Feger Jackson , killed in the Battle of Fredericksburg , Virginia , in December 1862 . Notable leaders from Pittsburgh . The greater Pittsburgh area was the birthplace or long - time residence of several Union army and navy officers , as well as some leading politicians of the era . Other important personalities of the Civil War born in the immediate Pittsburgh area included Col . Daniel Leasure , Congressman Robert McKnight , industrialist William Metcalf , and Brig . Gen . Thomas A . Rowley . Among the recipients of the Medal of Honor for gallantry in action during the war were Alexander Kelly , a free black who fought in the 6th U . S . C . T . . The mayors of Pittsburgh during the Civil War were George Wilson ( 1860 – 62 ) , Benjamin C . Sawyer ( 1862 – 64 ) , and James Lowry , Jr . ( 1864 – 1866 ) . Civil War attractions in Pittsburgh . The Soldiers and Sailors National Military Museum and Memorial is a National Register of Historic Places landmark . It is the largest memorial in the United States dedicated solely to honoring all branches of military veterans and service personnel .