mək hˈɛnɹi wʌz bˈɔːɹn mˈɛɹi ᵻlˈɪzəbəθ wˈɪljəmsən mˈɜːfi ɪn wˈɑːʃɪŋtən, dˈiː.sˈiː., tʊ ælphˈɑːnsoʊ wˈɪljəmsən hˌuː wˈɜːkt wɪððə lˈaɪbɹɛɹi ʌv kˈɑːŋɡɹəs ænd ᵻlˈɪzəbəθ bˈɛnɪt wˈɪljəmsən ɐ tˈiːtʃɚ.
McHenry was born Mary Elizabeth Williamson Murphy in Washington, D.C., to  Alphonso Williamson (who worked with the Library of Congress) and Elizabeth Bennett Williamson (a teacher).