•The Arch is the tallest national monument in the United States at 630 feet; it is the city’s best known landmark and a popular tourist attraction.
•Construction began February 12, 1963 and the last section of the Arch was put into place on October 28, 1965.
•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.
•Each year, approximately a million visitors ride the trams to the top of the Arch. The trams have been in operation for over 30 years, traveling a total of 250,000 miles and carrying over 25 million passengers.
•The Arch weighs 17,246 tons. Nine hundred tons of stainless steel was used to build the Arch, more than any other project in history.
•The Arch was built at a cost of $13 million. The transportation system was built at a cost of $3,500,000.
•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 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″.