Packer served in the Union Army, during the American Civil War. He enlisted on April 22, 1862 in Winona, Minnesota and was assigned to the 16th U.S. Infantry Regiment – Company F. He was honorably discharged due to epilepsy eight months later, at Fort Ontario, New York. He moved south and on June 25, 1863, enlisted in the 8th Iowa Cavalry Regiment – Company C, at Ottumwa, Iowa. However, he was discharged at Cleveland, Tennessee, on April 22, 1864, for the same reason. Packer suffered from seizures, secondary to his condition, and is reported as having had them about every two days – which ultimately led to his discharge.