Close-up view of the Gateway Arch, the symbolic gateway to the West (although there's a great deal of Midwest to go before the West is reached) and the centerpiece of the Jefferson National Expansion Memorial.
Designed by Finnish American architect Eero Saarinen and structural engineer Hannskarl Bandel, the stainless-stel arch opened to the public on June 10, 1967. At 630 feet, it is the tallest manmade monument in the United States. The cross-sections of the arch's legs are equilateral triangles, narrowing from 54 feet per side at the bases to 17 feet (per side at the top. Each wall consists of a stainless steel skin covering a sandwich of two carbon-steel walls with reinforced concrete in the middle from ground level to 300 feet , with carbon steel to the peak. The arch is hollow to accommodate a tram system that takes visitors to an observation deck at the top.