Dr. Myrtle Byram McGraw was born on August 1, 1899 in Birmingham, Alabama. As a child, McGraw took business courses and worked for a local Birmingham lawyer. Through these connections, she was educated at Snead Seminary in Boaz, Alabama, where her employer had arranged for McGraw to work as a secretary to fund her education. After Snead, McGraw attended Ohio Wesleyan University and graduated in 1923.

McGraw was heavily influenced throughout her career by the work of teacher, psychologist, and philosopher John Dewey (1859-1952), with whom she began a correspondence at age 15 after reading about him in a magazine. Dewey supported McGraw by hiring her to type a manuscript of his book after she graduated from Ohio Wesleyan. She used these funds to attend graduate school at Teachers College, Columbia University, studying religious education. After earning her Masters degree, she worked in Puerto Rico for one year before deciding to return to Teachers College to pursue doctorate study in psychology. She was supervised by Dr. Helen Thompson Woolley. In 1930, McGraw obtained her doctorate and was hired as associate director of the Normal Child Development Study at Babies Hospital, Columbia-Presbyterian Medical Center in New York City. With an emphasis on factors impacting growth processes rather than established norms of developmental milestones, McGraw worked closely with colleagues Frederick Tilney and George Coghill to develop new tests and methods of observation, often incorporating film into the studies. In 1932, McGraw began an intensive long-term study of the motor development of identical twins Johnny and Jimmy Woods. In 1935, she published her findings in "Growth: A Study of Johnny and Jimmy," her most cited work. In 1940, the Normal Child Development Study was closed due to the impending war. McGraw left the Babies Hospital in 1942 and published her second book, "The Neuromuscular Maturation of the Human Infant" the following year.

For the next decade, McGraw was focused on family life. She was raising a daughter, Mitzi, with her partner Rudolph Mallina, whom she had married in 1936. She returned to teaching in 1953 when Briarcliff College, a women's college in New York, offered her a position in their psychology department that allowed for a flexible schedule to accomodate McGraw's parenting duties. McGraw retired in 1972. She died on September 6, 1988.