As Robert E. Lee was preparing his invasion of the north in June 1863, citizens across Pennsylvania were in a state of panic. With news spreading of the impending Confederate advance, towns and cities across the Keystone State mirrored a sense of fear and uncertainty. These communities prepared for the worst, and began constructing defensive fortifications at a rapid pace.
Believed to be viable targets for Confederate forces, the city of Pittsburgh, as well as neighboring Allegheny City and Birmingham, began an aggressive assembly of defensive works. This region of western Pennsylvania served as an industrial and military hub, but also sat within 50 miles of enemy territory along the Pennsylvania/Virginia border. In addition, the Ohio River formed at the confluence of the Allegheny and Monongahela Rivers, and starting in Pittsburgh, served as an open highway to western states and territories.
On June 10, Secretary of War Edwin M. Stanton, a former Pittsburgh resident, wired to Assistant Adjutant General of Western Pennsylvania Thomas Howe, informing him of the departure of Major General William T.H. Brooks from Washington, headed for Pennsylvania. Brooks was to take command of the Department of the Monongahela upon his arrival in Pittsburgh, and quickly assemble a force capable of constructing a network of fortifications around the city.
The following Sunday, June 14, it was decided that all able-bodied men and manufacturers would be responsible for building earthworks under the direction of federal engineers. All work shops would subsequently close during the state of emergency, as well as any taverns or pubs that might distract the laboring citizens from their work. Nearly 16,000 residents would assist in the construction of Pittsburgh’s defensive system over the span of two weeks. In this time frame, 36 forts, redoubts, and batteries were erected from the western Pennsylvania soil.
Captain William Craighill, engineer and supervisor of the Pittsburgh defenses, wrote in his report,
"It is well known that when General Barnard arrived here the city was not supposed to be threatened by anything more serious than a raid of a few thousands of cavalry or mounted infantry, accompanied by light artillery. The instructions from Washington on which we acted looked to securing the city against attack. This has been done. We are, moreover, in a condition to make a vigorous defense against an army."
With the knowledge that Lee’s Confederate force was moving toward Pennsylvania, Thomas Howe issued an order on June 17, stating
“I desire again to call upon all good citizens in Western Pennsylvania capable of bearing arms to enroll themselves immediately into military organizations, and report to me for duty. If we would stay the march of the invader, we must be prepared to admonish him that we are fully organized and ready to receive him, in a manner becoming freemen, who cherish time-honored institutions, in defense of which so many of our sons and brothers have already offered their lives a willing sacrifice. Let us emulate their glorious example and never let it be written of us that we proved recreant in the hour of danger.”
Eventually, little more than 1,000 militia would be recruited as the city’s defenders.
Taking a retrospective look at the desperate situation several decades later, an 1894 edition of the Pittsburgh Post-Gazette reflected:
“Pittsburgh’s position is one that admitted of being strongly fortified, and an area enclosed that would support with comfort a very large body of troops, while at the same time the Ohio River furnishes facilities by which the whole western country could be controlled. Had it been captured there is but little doubt the confederate forces would have endeavored to have held the place. The facilities it contained for the manufacture of the munitions of war, its opportunities for receiving supplies from Canada, its capability of being strongly fortified, its strategical power as severing the West from the East, rendering thus very difficult the movement of troops between the two sections, would all have made it important for the confederacy to have held it if possible, and succeeding therein, caused perhaps a different ending to the civil war. Its capability for being fortified was so great that a commission of United States engineers who made an examination on this point in June 1861, pronounced it the strongest position they ever knew in the country.”