The St. Louis Arch is located in St. Louis, Missouri and was designed by American-Finnish architect, Eero Saarinen. The construction was completed in 1965, and is designated a national monument. The arch is 630 feet tall and is the tallest national monument in the United States. The arch symbolizes St. Louis’ role in westward expansion, posing as a “gateway” to the west. The cross-sections of steel are equilateral triangles. The arch is hollow to accommodate a tram system that allows visitors to ride to the top of the arch and stand on the viewing deck One struggle during construction was that the two sides did not meet in the middle near the end of construction. Additionally, an actuarial firm predicted that 13 workers would die during the construction of the arch, but thankfully, no workers died during the construction. The St. Louis Arch is a great example of the collaboration between engineers, mathematicians, and architects needed to create truly masterful structures.