What time of year is your flight?
I've looked at the AA.com web site for some dates in July and the only connx they show on PDX-ORD-GLA has you sitting at ORD for 6 hours. They do NOT show what is now a 30-minute connx. I think that is a very strong hint.
If I just ask for PDX-ORD they show a flight that arrives at 7:30 pm as well as the morning flight. The ORD-GLA departure is now 8:00 pm in early July.
I would NOT consider such a short connection.