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 and Missouri's tallest accessible structure. 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.