Eldest daughter of Cassius and Mary Jane Clay, Mary Barr Clay married Frank Herrick in October 1866 and had three sons between 1869 and 1871. They divorced in 1872 and she reclaimed her maiden name, also insisting that two of her sons take her surname.
Mary Barr Clay wrote to Lucy Stone’s Woman’s Journal in 1875, announcing that she was a “soldier of the cause, enlisted for the war.” She was a delegate for the NWSA convention in St. Louis in the spring of 1879 where she recruited Susan B. Anthony for a Kentucky lecture tour that October. She also served as vice president and president of AWSA in 1881 and 1883. In an 1884 speech to NAWSA, she said: “In talking to a Kentuckian on the subject of women’s rights, you have to batter down his self-conceit that he is just and generous and chivalric toward women.”