Good stuff ToughOmbre
You are quite lucky to have a clear picture of your father's service (plus actual pictures!!!)
Just a few clarifications you might find helpful. You list Riflemen which I imagine was his Military Occupational Specialty (MOS) for which he was trained and qualified. However there are few (if any) Riflemen in the Infantry Regiment Cannon Company. I imagine he was later assigned to the Cannon Company and OJT'ed (on the job trained) with another set of skills. Most enlisted men in the Cannon Company would be gun-crewmen which took few casualties and not much need for converted Riflemen. One other enlisted position that did take casualties and could use the skills of a Riflemen would be part of a Forward Observer Team, which would consist of an officer and few enlistedmen for radio operators and security. Working closely with the Rifle Companies an FO team needed to know their way around the front. I find it plausible that your father found his way to an FO team after service with a Rifle Company.
I am also curious if your father trained with the 90th Division from its activation or perhaps joined the Division later from an Infantry Replacement Training Center (IRTC)? From the date of your father's start of active service it might be possible to infer which route he took to the Infantry.
In any case, Best Wishes!!!!
You bring up some good points that got me thinking. I got the "Cannon Company" info off of his Bronze Star commendation. Not sure how accurate that is knowing how the army could confuse things. Anyway he definitely was a rifleman, but as you say, he could have been moved around, but I'm inclined to think that your question makes me think that the Cannon Company reference may be less than accurate. I remember him telling of how he often walked the "point" with his unit. And his war stories led me to believe he was in a rifle company.
As to his joining the 90th........Long story short.
He was an artillery instructor at Fort Sill OK. Got into a disagreement with his CO. CO transferred him into the 90th shortly after (or maybe before) they got their orders to deploy to the ETO. At least that's the best I can remember.
Sure wish he was still around to answer some of these questions, but in spirit he will always be with me.
Thanks again for your interest.