AC 523 then UA 3376 at O'Hare
Montréal → Chicago → St Louis
Timetable, Chicago time
15:00AC 523 from Montréal at the gate
11:00UA 3376 to St Louis leaves the gate
20 h apart on the timetable, overnight
UA 3376 leaves 20 h after AC 523 arrives on the timetable: more than half a day, so not a connection we count.