I see a double connection (via SJU and MIA) that departs STT at 12:15 PM, arriving STL at 10:05 PM. It has a five-hour layover in SJU, but would give the OP an extra three hours in STT.
AMERICAN AIRLINES OPERATED BY AMERICAN EAGLE/EXECUTIVE 5069 STT
St Thomas Island Dec 12, 2009
12:15 PM SJU
San Juan Dec 12, 2009
12:49 PM AT7 Economy
View Seats 68 N/A 11 hr
50 min
AMERICAN AIRLINES 2202 SJU
San Juan Dec 12, 2009
05:40 PM MIA
Miami Dec 12, 2009
07:25 PM 757 Economy
View Seats 1045
AMERICAN AIRLINES 2055 MIA
Miami Dec 12, 2009
08:15 PM STL
St Louis Dec 12, 2009
10:05 PM 757 Economy
View Seats 1068
Edited to add:
aa.com is also showing this itinerary, with the same departure and arrival times as above, but with a shorter connection in SJU, and a longer connection in MIA:
AMERICAN AIRLINES OPERATED BY AMERICAN EAGLE/EXECUTIVE 5069 STT
St Thomas Island Dec 12, 2009
12:15 PM SJU
San Juan Dec 12, 2009
12:49 PM AT7 Economy
View Seats 68 N/A 11 hr
50 min
AMERICAN AIRLINES 588 SJU
San Juan Dec 12, 2009
04:00 PM MIA
Miami Dec 12, 2009
05:50 PM 757 Economy
View Seats 1045
AMERICAN AIRLINES 2055 MIA
Miami Dec 12, 2009
08:15 PM STL
St Louis Dec 12, 2009
10:05 PM 757 Economy
View Seats 1068
Last edited by guv1976; Aug 6, 2009 at 12:19 pm