Of course ... it's the Gateway Arch in St. Louis! The Jefferson National Expansion Memorial Park was established on the banks of the Mississippi River, on December 21, 1935, to commemorate the westward growth of the United States between 1803 and 1890.  Of course, that growth goes back to the Louisiana Purchase.

The park features the Gateway Arch, designed by architect Eero Saarinen who won the design competition in 1947. The stainless steel structure rises 630 feet high from a 60-foot foundation and spans 630 feet at ground level. Its classic weighted catenary curve sways 1/2" - 1" in 20 mph wind. Construction on the nation's tallest memorial began in 1961 with the "topping out" in 1965 and dedication in 1966.
 

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