The Jefferson National Expansion Memorial is better know to all St. Louis natives as simply The Arch. The view from the top of The Arch is fantastic although I personally do not enjoy the ride up or down - perhaps just because I am afraid of heights and spend the ride worrying about how I would get out if the elevators broke!
I do enjoy the view once I get up to the top and it is always best to go during non-peak times so there are not so many people fighting for a viewing spot.
I recently was able to see the Lewis and Clark movie at The Arch and film was great. The photography was beautiful and it was interesting enough to hold the attention of the adults and children in the audience. I did learn quite a bit about the expedition that I did not know before.
The least impressive part of my Arch visit was the museum. I found the layout to be rather confusing and the exhibits, while authentic, were not very interesting. If you are already visiting to see the view and movie the museum is worth taking a look at but I personally don't think it is worth a trip by itself.