Ray (webmaster) on 3/26/2012 9:49:01 PM:
Don't know if you've seen this yet, but from the home page look for the link "How to get to Downtown St Louis and Mississippi River from the Katy Trail by bike" (next to the tiny picture of the Arch). This page lists a few different options. The information was assembled a few years ago, but is still accurate as far as I know. Any new suggestions are always welcome.
Good luck, and happy trails!