Miller received his country's highest award for bravery during combat, the Medal of Honor, for actions taken on July 3, 1863 during the Battle of Gettysburg.

[1] At the First Battle of Kernstown, Miller was promoted to corporal.

During the attack Miller sprang forward, killed the color guard of the 34th North Carolina, and took his flag.

When Miller's unit had regrouped, Pickett's Charge had begun, and he was able to help corral the color bearer of the 38th Virginia, taking his flag as well.

[1] The President of the United States of America, in the name of Congress, takes pleasure in presenting the Medal of Honor to Corporal John G. Miller, United States Army, for extraordinary heroism on 3 July 1863, while serving with Company G, 8th Ohio Infantry, in action at Gettysburg, Pennsylvania, for capture of two flags.