He practiced for one year at the St. Joseph's Hospital in Phoenix, Arizona, before going back to Illinois for some post-graduate herpetology work.
Between 1951 and 1953, Shannon was sent as a lieutenant to Korea, where although on active service in a war zone he still found opportunities to collect many reptile specimens.
Back in the U.S., he published many articles on venomous snake bites, venomology, and herpetology.
Shannon is commemorated in the scientific names of two lizards: Sceloporus shannonorum and Urosaurus graciosus shannoni.
The specific name, shannonorum, which is genitive plural, honors both Shannon and his wife.