Gateway Arch Factoid: It is officially named the Jefferson Expansion Memorial.
Factoid The Gateway arch was constructed months ahead of schedule.
Factoid: On the spur of the moment, an unofficial time capsule was added to the keystone section at the top of the arch. it is a 55 gallon drum filled with items from St Louis School children, welded shut with an air tight seal and welded under the floor of the keystone section by the lead welder on one side of the arch. There is no predetermined date for it to be opened and even most of the Museum staff at the memorial are not aware of it.
Factoid. When the final section was to be installed, the two legs were slightly out of alignment. They were forced into alignment by using hydraulic jacks and cables internally, resulting in a slight warping of the legs. If you stand about 30 feet from the north side of the north leg and look up it you can see the warp.
Factoid: two custom-built cranes were in the construction of the Arch.
Factoid: during the construction, high winds would often cause the arch to sway several feet. During these times it was not safe for the workers to get off the structure, so they had to ride it out, sometimes for hours.