Do you know where he was born? Do you know where he died? Do you know if he served in the Philipines before WW1? Do you know what rank he was? As a "Commander", he would be a Captain, Major, Lt Colonel or Colonel, depending on what he was a "Commander" of. Do you know what the "W" or "J" stand for?
I have found several "W. J. Mcdowell's" and "William J. Mcdowell's" on the 1900 Census...but not knowing a little bit more information it would be difficult to determine.
The unit of assignment you provided did not see combat in WW1 having arrived in France in Sep 1918. Where did you get your information? Any little bit could help. If you do know where he died you can send for a death certificate and get some additional information.