STL was a senior base but I believe a lot people left suddenly and as a result, a good chunk of April class was put in STL..

Even the May & June class may be stuck in STL for a couple of months...

You will be in training for almost 3 months, DEN will open in the mean while & a few senior FO's who commute from DEN will go there...

If STL is what you want, you may get it in a few months if not right away...