UA 4581 then AA 3484 at O'Hare
Knoxville → Chicago → St Louis
Timetable, Chicago time
11:39UA 4581 from Knoxville at the gate
09:30AA 3484 to St Louis leaves the gate
21 h 51 apart on the timetable, overnight
AA 3484 leaves 21 h 51 after UA 4581 arrives on the timetable: more than half a day, so not a connection we count.