The Gateway Arch, or Gateway to the West, is an arch that is the centerpiece of the Jefferson National Expansion Memorial in St. Louis, Missouri. It was built as a monument to the westward expansion of the United States. At 630 feet (192 m), it is the tallest man-made monument in the United States, Missouri's tallest accessible building, and the largest architectural structure designed as a weighted or flattened catenary arch.
Located on the west bank of the Mississippi River where the city of St. Louis was founded, the arch was designed by Finnish American architect Eero Saarinen and structural engineer Hannskarl Bandel in 1947. Construction began on February 12, 1963, and ended on October 28, 1965, costing US$13 million at the time ($90,491,005 today). The monument opened to the public on June 10, 1967.