The Gateway Arch, formerly known as the Jefferson National Expansion Memorial. The memorial was established to commemorate:

• The Louisiana Purchase, and the subsequent westward movement of American explorers and pioneers
• The first civil government west of the Mississippi River
• The debate over slavery raised by the Dred Scott case.

The Gateway Arch, also known as the “Gateway to the West”, is the tallest structure in Missouri.
It was designed by Eero Saarinen and structural engineer Hannskarl Bandel in 1947. The Arch was built between 1963 and 1965.
It is630 feet tall and 630 feet wide at its base. The legs are 54 feet wide at the base, narrowing to 17 feet at the arch. There is a unique tram system to carry passengers to the observation room at the top of the arch.