In early 1962, when the Port Authority of New York and New Jersey officially authorized a plan to build the World Trade Center in Lower Manhattan, it came just months after President John F. Kennedy announced the U.S. goal of sending astronauts to the moon. The vision for the seven-building complex—which would cost an estimated $470 million (more than $4 billion in today’s dollars) and include the two tallest buildings in the world—embodied that same brand of American optimism and ambition. The twin 110-story towers at the heart of the World Trade Center were designed to surpass New York’s iconic Empire State Building—then the world’s tallest building. Building the new towers would marshal unprecedented levels of design innovation, engineering prowess—and breathtaking risk.