Shannon later worked as treasurer and general manager of Lucas Manufacturing, a clothes-making business in Columbia owned by his wife's family.

Shannon received the Army Distinguished Service Medal at the end of the war, the citation for which reads: The President of the United States of America, authorized by Act of Congress, July 9, 1918, takes pleasure in presenting the Army Distinguished Service Medal to Colonel (Infantry) Edward C. Shannon, United States Army, for exceptionally meritorious and distinguished services to the Government of the United States, in a duty of great responsibility during World War I.

Maintaining at all times a high degree of efficiency in his regiment, he contributed materially to the success achieved by the 28th Division in its operations against the enemy, rendering services of distinction to the American Expeditionary Forces.

[2]He was also awarded the Silver Star, with the citation reading: By direction of the President, under the provisions of the act of Congress approved July 9, 1918 (Bul.

43, W.D., 1918), Colonel (Infantry) Edward C. Shannon, United States Army, is cited by the Commanding General, American Expeditionary Forces, for gallantry in action and a silver star may be placed upon the ribbon of the Victory Medals awarded him.

Colonel Shannon distinguished himself by gallantry in action while serving as Commanding Officer, 111th Infantry Regiment, 28th Division, American Expeditionary Forces, in action 24 July 1918, at the Foret de Fere, France, in personally reconnoitering in front of his lines under intense machine gun fire.