In January, the regiment transferred to Washington DC, went into camp on the Bladensburg Road (three miles from Washington), and drilled. The regiment remained at Washington in February, March, and April, with various duties, including guarding the Old Capitol Prison and the Long Bridge. The regiment then relieved the 88th Pennsylvania at Alexandria, where Colonel Gregory was acting Military Governor, and Captain Sinex was Provost Marshall. The regiment remained on duty in Alexandria in May, June, and July, with guard, patrol, and other duties. Morale was very low by the end of the summer.
But in August, they were relieved, and joined the Army of the Potomac. They initially camped near Cloud's Mills, Virginia. In September, they joined the main force of the Army of the Potomac, arriving at Antietam just after the fighting finished. After spending most of October in camp, they participated in a reconnaissance to Leestown Virginia, with a skirmish at Shepherdstown. The regimental wagon was captured when it was left behind at Snicker's Gap in November. The regiment moved to Warrenton, then encamped at Stoneman's Switch. They were part of the final attack on Marye's Heights in the Battle of Fredericksburg, in December. After that failed attack, the regiment helped cover the Union retreat, with pickets from company E the last Union forces to leave Fredericksburg, left behind by mistake.