“The famous escalator scene,” Trump himself would say. “It looked like the Academy Awards.”

What really went into that moment, and what was it like to experience? This oral history was assembled from reporters and photographers who were there; from Trump’s aides and advisers and former Trump Organization executives; from a lead architect and the construction manager of Trump Tower; from the co-author of The Art of the Deal and former contestants on “The Apprentice” as well as supporters and others who had seen Trump prepare and rehearse for this for decades.

They thought they knew who he was, and what he was doing, and how this would go. They had no idea.