This National Monument was built to symbolize the area of St. Louis as having been the “Gateway to the West”. St. Louis was one one the main starting places for the many families who made the trek to the west by wagon train since it was the gathering and supply location for many of the wagon trains that carried those who settled the western United States.
The “Arch” is the tallest National Monument in the USA, it stands 630 feet tall, and for a fee of $10 you can ride a elevator to the top and spend as long as you like looking out the observation windows on both sides.
The Arch is a structure known as a catenary curve, the shape a free-hanging chain takes when held at both ends, and considered the most structurally-sound arch shape. The span of the Arch legs at ground level is 630 feet, the same as its height.
Construction began February 12, 1963 and the last section of the Arch was put into place on October 28, 1965.
In order to ensure that the constructed legs would meet, the margin of error for failure was 1/64th of an inch. All survey work was done at night to eliminate distortion caused by expansion from the sun’s rays. Since the Arch was constructed before the advent of computer technology, relatively crude instruments were used for these measurements.
The Arch sways a maximum of 18" (9" each way) in a 150 mph wind. The usual sway is 1/2".
(Source – LINK)
*This view of the arch is taken from the cobblestone riverfront area near the edge of the Mississippi River.
Nikon D40X with Nikon 18mm X 55mm Lens ~ Focal length 10mm ~ f6.5 ~ ISO 125
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