The Gateway Arch, designed by Eero Saarinen, is only part of the Jefferson National Expansion Memorial. The memorial also includes St. Louis's Old Courthouse, and the Museum of Westward Expansion, located underground at the feet of the Arch. The Old Courthouse has been standing since 1839, was the site of the Dred Scott case and is now a museum to the history of St. Louis. The Museum of Westward Expansion is an area nearly as large as a football field, housing many items preserved since the Mississippi River was the western frontier of America.
The Arch itself is the United States of America's tallest national monument, standing 630 feet high. Because it is a catenary arch, the span between its legs at the bottom is the same 630 feet. It is the fourth most-visited tourist attraction in the world, with as many as 6,000 people per day riding the specially-built trams up either leg to the observation area at the top. In the event of an emergency, an emergency stairway of 1,067 steps run up either leg. The Arch may be, however, safer than the ground: its lightning rods are rooted firmly in the bedrock below, its legs are anchored 60 feet below ground, and is built to survive earthquakes and flexing up to 18 inches in 150 mile per hour winds.
Construction on the Arch was completed with the keystone section, placed on October 28, 1965. Although the dangers of construction predicted 13 deaths, the Gateway Arch was completed with no casualties. It weighs in at over 17,000 tons, and is made up of 142 pieces of stainless steel. Sadly, all of those near the ground are virtually covered in decades of scratched-in graffiti. The Arch cost a total of $13 million, over $2.5 million of which went towards the trams running through the legs.
Danke schön cbustapeck for the architect's name.