Their first action was a skirmish with the sheriff of Tyler County, West Virginia; the regiment was to hunt down and arrest him, as he was a Confederate sympathizer. The 7th fought in the 1862 Valley Campaign in Nathaniel Banks' V Corps, seeing action in a number of small engagements before fighting in the Battle of Port Republic in late May. It was assigned to the II Corps and would remain in that organization for the rest of the war. A part of Nathan Kimball's brigade during the September 1862 Maryland Campaign, the 7th West Virginia took part in the attack on the Sunken Road ("Bloody Lane") at Antietam. Following the battle, the regiment helped garrison Harper's Ferry until the end of October, when it marched through the Loudoun Valley to Falmouth, Virginia. The 7th next saw action at the Battle of Fredericksburg in the II Corps assault, and participated in the ill-fated Mud March.