A completely free-standing 33-story building, in 1909 Liberty Tower was the tallest building in the world with such a small footprint. Because the then new principles of "skyscraper" design were not yet fully understood, the building was overbuilt, with its steel foundation anchored deeply into bedrock five stories below street level.
This overly sturdy construction helped this tall, slender building withstand the collapse of two World Trade Towers only 220 yards to the west on September 11, 2001, with only minimal damage despite the impact which was measured at the time as a 3.3 magnitude seismic event.
