World Almanac

In 1889, Paris hosted an Exposition Universelle (World’s Fair) to mark the 100-year anniversary of the French Revolution. More than 100 artists submitted competing plans for a monument to be built on the Champ-de-Mars, located in central Paris, and serve as the exposition’s entrance. The commission was granted to Eiffel et Compagnie, a consulting and construction firm owned by the acclaimed bridge builder, architect and metals expert Alexandre-Gustave Eiffel. While Eiffel himself often receives full credit for the monument that bears his name, it was one of his employees—a structural engineer named Maurice Koechlin—who came up with and fine-tuned the concept. Several years earlier, the pair had collaborated on the Statue of Liberty’s metal armature.

Eiffel reportedly rejected Koechlin’s original plan for the tower, instructing him to add more ornate flourishes. The final design called for more than 18,000 pieces of puddle iron, a type of wrought iron used in construction, and 2.5 million rivets. Several hundred workers spent two years assembling the framework of the iconic lattice tower, which at its inauguration in March 1889 stood nearly 10,000 feet high and was the tallest structure in the world—a distinction it held until the completion of New York City’s Chrysler Building in 1930. (In 1957, an antenna was added that increased the structure’s height by 65 feet, making it taller than the Chrysler Building but not the Empire State Building, which had surpassed its neighbor in 1931.) Initially, only the Eiffel Tower’s second-floor platform was open to the public; later, all three levels, two of which now feature restaurants, would be reachable by stairway or one of eight elevators.
( Source:http://www.history.com/topics/eiffel-tower )