The Freemasons were a fraternal organization formed in the late 16th or early 17th century, which permitted men of any religion to join. Some of the commanding officers on both sides of the American Revolutionary War were members, and several Presidents of the United States have been members of Lodges.
- "No private Piques or Quarrels must be brought with in the Door of the Lodge, far less any Quarrels about Religion, or Nations, or State-Policy, we being only, as Masons, of the Catholick Religion above-mention’d ; we are also of all Nations, Tongues, Kindreds, and Languages, and are resolv’d against all Politicks."
- ―Clause VI. Of Behavior.[src]
To join a Lodge, one had to be a male citizen of sound mind and body, and to have good character. One's religious denomination did not matter, and similarly political and religious discussions were not allowed between them. Freemasons were informed not to become rebels of the state, though doing so were not grounds for expulsion.
Advancing through the Lodge was based on merit, not their place in society. The degrees of Masonry were as follows: Fellow-Craft, Warden, Master of a local Lodge, Grand-Warden, and finally Grand Master of the Lodge. Craftsmen were to respect and obey their Masters in completing their work. As a Brotherhood, Masons were to show respect to one another, to not show jealousy or complete another's designated task for themselves to gain favor with the Master, or to dispute the Master's decisions over wages, or to interrupt him, nor could they hold private deliberations without his permission.
Outside a Lodge, Masons were to treat each other with the same respect and rank in private. If they met a Mason from another Lodge, they were to be discreet, should they be an imposter, and if they were genuine, then a Mason should be respectful but careful not to instruct them more than was appropriate. Among non-Masons, including family, friends or strangers, they were to be discreet about the Lodge but stay true to its principles.
To remain unnoticed by British soldiers in Boston and New York, the Freemasons moved around in underground tunnels. The Masons placed metal engravings of the Square and Compasses on their floor, which would point the way out when lit.
During the 18th century, Haytham Kenway and Connor explored the tunnels and came across some exits which required the magic lantern to be unlocked. To determine the placement of projected images on the door, Connor analyzed pages from The Charges Of a Free-Mason, which had capitalized clues inserted into the text. For example, the quotation from Clause VI. had the phrase "To the left of all nations" after the mention of the Catholic religion.
- Alex Hutchinson confirmed that in the Assassin's Creed universe, the Freemasons are "just boring guys who have meetings", and are not branches of the Assassins or Templars.
- The Masonic manuscripts Connor finds are taken from Benjamin Franklin's 1734 reprinting of the first printed constitution by James Anderson.