WN 209 then UA 645 at Denver
St Louis → Denver → Sioux Falls
Timetable, Denver time
18:50WN 209 from St Louis at the gate
17:25UA 645 to Sioux Falls leaves the gate
22 h 35 apart on the timetable, overnight
UA 645 leaves 22 h 35 after WN 209 arrives on the timetable: more than half a day, so not a connection we count.