Department of the Susquehanna The Department of the Susquehanna was a military department created by the United States War Department during the Gettysburg Campaign of the American Civil War . Its goal was to protect the state capital and the southern portions of the commonwealth of Pennsylvania , and to deny the Confederate army passage across the vital Susquehanna River . Gettysburg Campaign . On June 9 , 1863 , President Abraham Lincoln , responding to Robert E . Lee ' s impending invasion of Maryland and Pennsylvania , called for 100 , 000 volunteers from Pennsylvania , New York , and Ohio to help repel the invasion , with only about 33 , 000 recruits answering his call . Secretary of War Edwin M . Stanton ordered the creation of two military departments , the Departments of the Susequehanna and Monongahela , to organize these militia and defend the state of Pennsylvania . The Department of the Susquehanna consisted of all troops east of Johnstown and the Laurel Highlands , and it was initially headquartered at Chambersburg . It was placed under the command of Major General Darius N . Couch , who had formerly commanded II Corps , Army of the Potomac . As the Confederates entered the Cumberland Valley , Couch moved his headquarters to Harrisburg . Militia from New York and New Jersey arrived in the capital to provide manpower while the newly raised Pennsylvania emergency militia drilled at Camp Curtin . New York troops serving under the Department of the Susquehanna were first engaged in a skirmish with Confederate cavalry under Albert G . Jenkins at Greencastle on June 20 , losing one man killed ( considered the first casualty of the Gettysburg Campaign on Northern soil ) . The New Yorkers eventually retired to Harrisburg , allowing Jenkins to occupy Chambersburg . Couch ordered that no Confederate unit was to be allowed to cross the Susquehanna River . He authorized the construction of earthworks and fortifications near Lemoyne to defend Harrisburg and its river bridges . He assigned William F . " Baldy " Smith to defend the state capital . Couch designated his aide - de - camp , Major Granville O . Haller , as the sector commander to defend Adams and York counties , with regional headquarters in Gettysburg . Couch sent out three regiments of state emergency militia to Haller ' s assistance , with the 26th Pennsylvania Volunteer Militia ( P . V . M . ) sent to Gettysburg , the 20th P . V . M . to York County , and the 27th P . V . M . to Columbia to defend the Columbia - Wrightsville Bridge , a vital crossing over the Susquehanna . On June 26 , 1863 , advancing Confederates under Jubal Early and John Brown Gordon routed Haller ' s militia at Gettysburg and occupied the borough . Haller retired to York , which surrendered on June 28 , becoming the largest Northern town to fall during the Civil War . Prior to the Confederate occupation , Haller removed his troops to Wrightsville , where in obedience to Couch ' s orders , Haller ordered the covered bridge burned to prevent Confederate passage into Lancaster County . The troops of the department assigned to General Smith took part in skirmishes against elements of Richard S . Ewell ' s corps in Cumberland County at Sporting Hill on June 30 and against J . E . B . Stuart at Carlisle on July 1 . Couch dispatched Smith ' s men , along with many of Haller ' s , to help George G . Meade pursue Robert E . Lee ' s retreating Army of Northern Virginia . The Department of the Susquehanna remained operational following the conclusion of the campaign , although many of the militia were sent home . Subsequent actions . With the threat repelled , Couch moved his headquarters back to Chambersburg , and the department played an administrative role the rest of the year , providing militia to help clean up the Gettysburg Battlefield and assisting in the military preparations for the dedication of the Gettysburg National Cemetery and Lincoln ' s visit , which resulted in the Gettysburg Address . In January 1864 , Couch responded with troops to rumors that a band of disgruntled constituents planned to prevent the inauguration of Pennsylvania Governor Andrew Curtin . In March , with rumors rife of yet another raid , Couch made preparations to again defend the state . However , it was not until late July when the Confederates again arrived in Pennsylvania , when John McCausland raided and burned Chambersburg . Couch was again engaged in sending out 100 - day volunteers , militia and Federal troops to repel the enemy . In September , the department dispatched troops to various locations to help oversee the military draft . The following month , the department again responded to a threatened Confederate border raid . Philip H . Sheridan ' s subsequent victories in the Valley Campaigns of 1864 finally removed any further threats . The Department of the Susquehanna remained in existence until December 1 , 1864 , when it was merged with the Department of the Monongahela into the Department of Pennsylvania .