From Surviving Records maintained by the National Personnel Records Center, St Louis, MO.
PFC Carlson's official records were partially destroyed by the fire in St Louis on 12 July 1973. The below is based upon information in the surviving records provided by the NPRC.
Certificate of Military Service
This certifies that Charles August Carlson, 1 183 428, was a member of the United States Army from December 12, 1917 to February 18, 1919. Service was terminated by Honorable Discharge.
PFC Charles A. Carlson accepted enlistment at Havre, Montana.
He enlisted in the US Army Air Service, Signal Corps at Fort George Wright, Washington on 12 December 1917 for a "Period of the emergency unless sooner discharged".
His enlistment assignment was the 23d Balloon Company, Air Service and was initially assigned the 2nd Training Brigade, Kelly Field, San Antonio, Texas.
Upon completion of his training at Kelly Field, he was assigned to Camp MacArthur Waco, Texas with the 23d Balloon Company in March 1918.
On 1 May 1918, the 23rd Balloon Company was stationed at Post Field, Fort Sill, Oklahoma and started their training schedule which included Field Service Regulations, Manual of Interior Guard Duty, Infantry Drill Regulations, Telephones, Windlass, Balloons and Machine Guns. Training was scheduled to be completed by 1 July 1918. (Aerial Age Weekly Vol 15, Page 374, 26 June 1922)
Records indicated that his foreign service was from 21 October 1918 to 21 January 1919. He departed France from the port of Brest in January 1919 and assigned to Camp Devens, MA. From Camp Devens,he was transferred to Camp Lewis, Washington for the purpose of being processed for discharge. He was discharged on 18 February 1919.
I remember him telling me that his duties in France were to man the machine gun which guarded the base device which held the observation balloon. As I recall he said they landed in Brest and were stationed in the vicinity of Nancy.
I wish I had been more interested at the time to try to extract information from him. SGM Charles R. Carlson (his son)