Mallon, as Isabel Sloan, was born in Baltimore, Maryland in 1857. When her husband William Mallon became ill (and later died), she pursued journalism for income, starting by writing about fashion. She started the "Bab's Babble" gossip column for newspaper syndication, starting with the New York Star, in 1888.
The "Ruth Ashmore" column was conceived of by Edward W. Bok, who after taking over the Journal in 1888.
Mallon died from pneumonia in New York City on December 27, 1898. Although Bok recalled in his autobiography that Mallon wrote as Ashmore for 16 years, it appears to have been closer to nine.