UA 375 then UA 3376 at O'Hare
Boston → Chicago → St Louis
Timetable, Chicago time
15:32UA 375 from Boston at the gate
11:00UA 3376 to St Louis leaves the gate
19 h 28 apart on the timetable, overnight
UA 3376 leaves 19 h 28 after UA 375 arrives on the timetable: more than half a day, so not a connection we count.