stevie from saint louis on 2/24/2009 11:24:18 PM:
I believe that Babler State Park in St. Louis County allows trailer or RV camping. It is managed by the Missouri Department of Natural Resources, who would have more info. However, from there, you still would have about a 10 mile commute to the nearest Katy TrailHead. It is still about $20 for a camping spot with an electric hookup.
I have also seen an occasional RV at the Matson Trailhead. It is a very large parking area, and it has maybe a half a dozen vehicles on a busy weekend. Camping is not allowed at Trailheads, but as long as you don't do something to draw attention to yourself, I doubt anyone would bother you there.