Commuters, New Yorkers and tourists who would ordinarily brush past each other on their way through Grand Central Terminal gathered on Friday in the middle of the main concourse to commemorate the station's 100th birthday. Speakers at the ceremony included Mayor Michael Bloomberg and Caroline Kennedy, whose mother, Jacqueline Kennedy Onassis, was instrumental in the effort to stop a skyscraper from being built above the landmark in the 1970s. Several speakers also noted that former Mayor Ed Koch, who died Friday morning, had also played a role in helping save the station. Mr. Bloomberg went further, crediting Mr. Koch with having "made the city what it is today." The mayor, who hopes to pass a massive midtown rezoning designed to spawn a new generation of skyscrapers in the area before leaving office, pointed out that while the station's preservation is to be celebrated, other spaces should be permitted to redevelop. "Grand Central was built to have commerce develop around it," the mayor said. "We have to make sure it remains a vital part of our growth." Caroline Kennedy noted that her mother would no doubt agree with that. "She understood how great public spaces can create community and knew that soaring architecture can nourish the spirit," Ms. Kennedy said.