AA 6255 then UA 3376 at O'Hare
Sioux Falls → Chicago → St Louis
Timetable, Chicago time
17:30AA 6255 from Sioux Falls at the gate
11:00UA 3376 to St Louis leaves the gate
17 h 30 apart on the timetable, overnight
UA 3376 leaves 17 h 30 after AA 6255 arrives on the timetable: more than half a day, so not a connection we count.