In May 1879 during the National Woman Suffrage Association convention, Mary Barr Clay met Susan B. Anthony and became the Kentucky delegate for that organization, serving as a vice-president. She was already a Vice President for the American Woman Suffrage Association. Returning home she organized the Fayette County Equal Suffrage Association in 1879. The next year, she created the Madison County Equal Rights Association with charter members Mrs. Rollins Burnam, Mrs. Mary Ann Collins, Mrs. Lester Sommers, Mrs. E.E. McCann and Mrs. Martha Haley. Mary B. Clay was also the first Kentucky woman to speak publicly on women's rights.
A Woman of the Century: Fourteen hundred-seventy biographical sketches accompanied by portraits of leading American women in all walks of life (Cambridge: Harvard University, 1893): 179–180.
Fred A. Engle, Jr. and Robert N. Grise, Madison's Heritage Rediscovered: Stories from a Historic Kentucky County (Charleston, SC: The History Press, 2012): 44.