Justin Matthews Glenn was born in Little Rock, Arkansas, and raised in Glendale and Phoenix, Arizona. He graduated from Stanford University (B.A., Classics, 1967; magna cum laude, Phi Beta Kappa) and was a Woodrow Wilson Fellow at Princeton University (M.A., Classics, 1969; Ph.D., Classics, 1970). He was a professor of Classics at the University of Georgia and Florida State University for 35 years, and he has published 70 articles, notes, and reviews in his field.
His ten-volume book The Washingtons, A Family History collects over 63,000 direct descendants of the immigrant John Washington, great-grandfather of George Washington. Since 2002 Glenn has served as Registrar General of The National Society of the Washington Family Descendants. He and his wife Jody reside in Tallahassee, Florida.