Cityfile.com has put together a brief list of major events and notable moments in the history of the Plaza.
October 1, 1907
 The Plaza first opens to the public. Designed by Henry Janeway Hardenbergh, it costs $12.5 million to construct.

1943 
Conrad Hilton buys the hotel for $7.4 million.

1955
 Kay Thompson’s Eloise is first published.

1964
 The Beatles stay at the Plaza during their first trip to the US.

1966 
Truman Capote hosts his Black and White Ball in the hotel’s Grand Ballroom.

1969 
The Plaza’s exterior is designated a New York City landmark.

1988
 Donald Trump buys the hotel for $390 million.

1995
 Trump sells the Plaza to Singapore-based businessman Kewk Leng Peng and Saudi prince Walid bin Talal for $325 million.

2004
 The Plaza is purchased by Israeli mogul Yitzhak Tshuva’s El-Ad Properties for $675 million. Miki Naftali is charged by Tsuhuva with overseeing the property.

Early 2005 
El-Ad closes the Plaza for renovations. Protests lead El-Ad to change its original plan to turn the entire building into condos, and reserve a portion of the property for hotel rooms.

Late 2005
 Condos in the building first go on sale.

October 1, 2007
 The 100th anniversary of the Plaza is celebrated with fireworks and a one-ton cake fashioned in the building’s image.

January 2008
 The first residents of the condo section of the building begin moving in.

March 1, 2008
 After three years and $400 million worth of renovations, the Plaza officially reopens to the public.
July 2008
The Plaza’s Rose Club opens.

September 2008 
Russian financier Andrei Vavilov files the first major lawsuit against El-Ad demanding the return of his $10.7 million deposit.

October 2008
 Boutiques begin opening as part of the Plaza Retail Collection.

Via Cityfile