The three founders, Dr. William Robert Woodman, William Wynn Westcott, and Samuel Liddell MacGregor Mathers were Freemasons and members of Societas Rosicruciana in Anglia (S.R.I.A.), an appendant body to Freemasonry. Westcott, also a member of the Theosophical Society, appears to have been the initial driving force behind the establishment of the Golden Dawn.
Influences on Golden Dawn concepts and work include: Christian mysticism, Kabbalah, Hermeticism, Paganism of Egypt, Theurgy, Freemasonry, Alchemy, Theosophy, Eliphas Levi, Papus, Enochian magic, and medieval grimoires.
Reference: goddesses-and-gods.blogspot.com