UA 4524 then UA 3907 at Houston
St Louis → Houston → Washington
Timetable, Houston time
11:01UA 4524 from St Louis at the gate
07:00UA 3907 to Washington leaves the gate
19 h 59 apart on the timetable, overnight
UA 3907 leaves 19 h 59 after UA 4524 arrives on the timetable: more than half a day, so not a connection we count.