Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge Visit The National September 11 Memorial Museum [Getty Images]

NEW YORK, NY - DECEMBER 09: Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge gaze at a commemorative installation during a visit the National September 11 Memorial & Museum on December 09, 2014 in New York City. The couple, who are traveling without their son Prince George, are on a three-day US east coast visit. This is the Duke and Duchess' first official visit to New York City. (Photo by Jonathan Brady - Pool/Getty Images)

Getty Images News Pool