The Gateway Arch is an arch that stretches 630 feet high and 630 feet long in St. Louis Missouri. The reason they chose the arch shape was because in 1947 and 1948 there was a competition to design a monument.. Eero Saarien won with his arch design, it was built to honor the western pioneers, and celebrate St. Louis’s role in the westward expansion of the USA. The construction of it started on February 12,1963. They built both legs of it up at the same time, the foundations for the legs go down 60 feet. This makes it very stable and able to sway up to 18 inches on 150 mph winds. It is made up of 142 12 foot stressed steel sections. Once set the sections had concrete poured into them leaving a hollow tube in them.The concrete only goes up
