The Gateway Arch is a 630-foot (192 m) high monument in St. Louis, in the U.S. state of Missouri. Clad in stainless steel and built in the form of a flattened catenary arch, it is the tallest man-made monument in the United States, Missouri's tallest accessible building, and the world's tallest arch. Built as a monument to the westward expansion of the United States, it is the centerpiece of the Jefferson National Expansion Memorial and has become an internationally famous symbol of St. Louis.
The arch sits at the site of St. Louis' foundation on the west bank of the Mississippi River. The Gateway Arch was designed by Finnish-American architect Eero Saarinen and German-American structural engineer Hannskarl Bandel in 1947. Construction began on February 12, 1963, and was completed on October 28, 1965, at a total cost of US$13 million ($96,300,000 in 2013). The monument opened to the public on June 10, 1967.