Where did Jackie O live?

Jackie O, formally known as Jacqueline Kennedy Onassis, lived at 1040 Fifth Avenue in New York City. This location was significant not only because it was her residence but also because it represented an important part of her life after her time in the White House. The apartment is situated on the Upper East Side, an affluent neighborhood that aligns with her social status and connections. Jackie O's time at 1040 Fifth Avenue allowed her to remain in the public eye while also providing her a sanctuary in one of the most renowned cities.

The other locations mentioned do not have a historical connection to Jackie O. 1000 Madison Avenue, 750 Park Avenue, and 555 Central Park West are notable addresses in New York City but are not recognized as her residence. Thus, 1040 Fifth Avenue is the correct answer, reflecting her life and legacy in the city.