Eero Saarinen's 1965 St Louis catenary — 192 m stainless-steel monument to westward expansion.
The Gateway Arch is a 630-foot-tall (192 m) monument in St. Louis, Missouri, United States. Clad in stainless steel and built in the form of a weighted catenary arch, it is the world's tallest arch, Missouri's tallest accessible structure, and no building can be taller than the arch in the St. Louis area. Some sources consider it the tallest human-made monument in the Western Hemisphere. Built as a monument to the westward expansion of the United States and officially dedicated to "the American people", the Arch, commonly referred to as "The Gateway to the West", is a National Historic Landmark in Gateway Arch National Park and has become a popular tourist destination, as well as an internationally recognized symbol of St. Louis.