I have shot several weddings that have the wedding ceremony at one location and the reception at another. This is pretty common, and is normal or par for the course. The bride and groom will often block off some time to go to yet another location(s) like a park to get some stunning photographs. This can be problematic if the location is far away from the wedding or reception location.
So, for example, you might block off two hours to get some extra shots but forget to factor the drive time or worse, the traffic jam. I have seen this time and time again. More reasons to work through your timeline with your wedding photographer. No photographer can predict a traffic jam in St Louis but we might have other routes to get to those locations or we may suggest other locations closer to your reception.
I am a St Louis wedding photographer that knows the market and area in and out of the St Louis metro. Other problems can arise from too many people at the location. It seems like Saturdays are the most popular day for weddings. This means hundreds of people flock to the Arch or places like Forest Park. Maybe find a location less busy with the Arch in the background or a smaller park with the same photo opportunities. So don't lose valuable photography time by choosing difficult or spread out areas...keep your locations close to the reception and factor times to utilize the timeline.