Dana led his brigade notably during the Battle of Antietam near Sharpsburg, Maryland, on September 17, 1862, where he was severely wounded. At Antietam, Dana and his brigade (part of Brig. Gen. John Sedgwick's 2nd Division of Maj. Gen. Edwin Vose Sumner's II Corps) forded the Antietam Creek at about 7:30 a.m. and marched to the support of the right of the Union line. Sumner ordered Sedgwick's division to form three parallel lines of battle, with Dana's men making up the second line. Sumner led this division due west, desiring to push any remaining Confederate forces through Sharpsburg and toward the Potomac River. They entered what is now called the East Woods, across the Hagerstown Turnpike, and into the area known as the West Woods.