In October 1861, Dana was appointed as colonel of the First Minnesota Infantry. He commanded this regiment at the Battle of Ball's Bluff. In Spring 1862, he was commissioned as a brigadier general. At the Battle of Antietam, he was wounded, and did not return to duty until July 1863. He returned to service as a major general, but he saw no more active duty, allocated to inactive theaters of operation. He resigned in May 1865.
