St Louis , U . S . A Spectators watch from across the Mississippi river as the final keystone section is hoisted to the top of the Gateway Arch here October 28th . Symbolizing the gateway to the west , the 650 foot high arch is the Nation 's tallest monument . when complete it will house restaurant and six car elevator . Made of stainless Steal anis is known officially as the Jefferson National Expansion Memorial . 2 November 1965