Baldridge, 86, had been living at the Surprise at Sunset Hill in Bethesda, The Washington Post reported.
The daughter of an Iowa congressman, Baldridge met the future Jacqueline Bouvier Kennedy at Miss Porter's School in Farmington, Conn. After graduating from Vassar, she served as social secretary to two U.S. ambassadors, David Bruce in Britain and Clare Booth Luce in Italy, and put in a stint as public relations director of the New York jeweler Tiffany.
In 1960, Kennedy invited Baldridge to work in the White House. President John F. Kennedy nicknamed her "Miss Push and Pull" because of her efforts to get him to conform to the customs of foreign leaders he met.
Baldridge left the White House in 1963, although a few months later she helped Jacqueline Kennedy plan her husband's funeral. She married Robert Hollensteiner and had a daughter.
While Baldridge went on to write memoirs and books about etiquette and to run her own public relations firm, her White House years remained central to the public view of her.