399 Park Avenue is a 41-story office building that from 1961 to 2015 was the world headquarters of Citigroup in Manhattan, New York City. The company moved into the building from 55 Wall Street in 1961, and from there to 388 Greenwich Street in 2015. 399 Park Avenue occupies the entire block between Park Avenue and Lexington Avenue and 53rd Street and 54th Street. The building lot was assembled by Vincent Astor who initially planned to build a 46-story Astor Plaza on the site.