AA 2762 then UA 3376 at O'Hare
Denver → Chicago → St Louis
Timetable, Chicago time
16:00AA 2762 from Denver at the gate
11:00UA 3376 to St Louis leaves the gate
19 h apart on the timetable, overnight
UA 3376 leaves 19 h after AA 2762 arrives on the timetable: more than half a day, so not a connection we count.