Ennis received the country's highest award for bravery during combat, the Medal of Honor, for his action during the Third Battle of Petersburg in Virginia on 2 April 1865.

He enlisted into the 1st Rhode Island Light Artillery.

[3] He died on 29 December 1930 and his remains are interred at the White Brook Cemetery in Rhode Island.

The President of the United States of America, in the name of Congress, takes pleasure in presenting the Medal of Honor to Private Charles D. Ennis, United States Army, for extraordinary heroism on 2 April 1865, while serving with Company G, 1st Rhode Island Light Artillery, in action at Petersburg, Virginia.

Private Ennis was one of a detachment of 20 picked artillerymen who voluntarily accompanied an infantry assaulting party and who turned upon the enemy the guns captured in the assault.