Harriet Lane Cates Hardaway was born in St. Louis in 1904, the daughter of John Mullanphy Cates and Elizabeth LaMotte Cates. Her father was a great-grandson of St. Louis businessman and philanthropist John Mullanphy through his mother, Catherine Clemens Cates, herself a
daughter of Elizabeth Browne Mullanphy and James Clemens Jr.
Harriet, called Dot, graduated from Maryville Academy in 1922. In April of 1932 she married Colonel Francis Page Hardaway, the widower of her sister Lucille M. Cates Hardaway, in the Panama Canal Zone. Harriet Hardaway had no children.
Harriet Hardaway apparently took over her cousin Mary C. Clemens's genealogical materials sometime in the 1950s upon the latter's death. She herself produced genealogical writings and kept up the additions and revisions to the genealogical research notes that Clemens had initiated. Hardaway seems to have bequeathed at least this part of her estate to her niece Elizabeth Tilton Seeley, who donated it to Saint Louis University in 1994 after Hardaway's death.