12th Pennsylvania Infantry Regiment  The 12th Regiment Pennsylvania Volunteer Infantry was an infantry regiment of the Union Army in the American Civil War. Raised in Pittsburgh and its surrounding counties in April 1861 for three months of service, the regiment spent its first month in training, then guarded the Northern Central Railway in Maryland until it was mustered out. Many of its men went on to serve in subsequent Pennsylvania regiments during the war. The 12th Pennsylvania was raised in Pittsburgh in April 1861 for a three-month term in response to President Abraham Lincoln's call for 75,000 men, under the supervision of Brigadier General James S. Negley. It was organized in that city on 22 April when its field officers were elected, with David Campbell, former captain of the Duquesne Grays, becoming its colonel. The regiment was partially based on the preexisting Pittsburgh militia companies known as the Duquesne Grays (Company B) and Jackson Independent Blues (Company A), some of whose members were Mexican–American War veterans, and the recently established Zouave Cadets (Company I) and City Guards (Company K). The remaining companies were formed from inexperienced volunteers: Company E (Washington Invincibles) at Washington, Companies F (Lawrence Guards) and H (Lawrence Guards) at New Castle, Company G (Monongahela Artillery) at Monongahela City, and Companies C (Firemen Legion) and D (Union Guards) at Pittsburgh. The 12th became the first regiment to depart the city on 24 April and arrived at Harrisburg on the next day, being quartered in churches and the Pennsylvania State Capitol. It was reviewed by state Governor Andrew Gregg Curtin in the afternoon alongside the 13th Pennsylvania Infantry before being mustered into Federal service. The regiment promptly entrained on the Northern Central Railway for Camp Scott near York, where it spent the next several weeks training. Conditions at Camp Scott, described by Samuel Penniman Bates' postwar official history as a "field of mud," made many of its men eager for action. The 12th received uniforms and equipment on 19 May, and relieved the 1st Pennsylvania Infantry along the Northern Central from the Pennsylvania–Maryland border to Baltimore on 25 May; the Northern Central provided an important connection between Harrisburg and points further north, Baltimore, and Washington, D.C. to the south. Regimental headquarters and Companies I and K were located at Cockeysville, while the remaining companies were spread out along the railroad; it was assigned to the 3rd Brigade of the 1st Division of Patterson's Army (the Department of Pennsylvania).