Her desire to be unchallenged chatelaine of American high society, at least in Newport and New York, was aided by the social climber Ward McAllister, who invented the conceit that there were 400 people who really mattered in society, that being the capacity of Mrs. Astor's ballroom. That her husband, William Backhouse Astor Jr, didn't care for the social whirl did not deflect her one iota. In 1883 she was reluctantly moved to admit Alva, Mrs. William Kissam Vanderbilt, to her social circle as the Vanderbilts had become too rich to ignore.
On the death of her brother-in-law John Jacob Astor III in 1890, his son William Waldorf Astor (1848-1919) attempted to challenge Caroline's right to be the one Mrs. Astor and insist that she be Mrs. William Astor. Caroline's success was such that that September William Waldorf Astor and his wife emigrated to Great Britain, where he later became 1st Viscount Astor.
Her nephew then had his father's house, 350 Fifth Avenue, torn down and replaced by the first Waldorf Hotel. Caroline, not willing to live next to a hotel at the old 340 Fifth Avenue, moved uptown to a more opulent mansion built at 840 Fifth Avenue (her son John Jacob Astor IV built the Astoria hotel at 340 and the two later merged before moving to the present location of the Waldorf-Astoria Hotel).
By the time she moved to the new house her husband had died; she died there herself at age 77.