A 1705 governor's residence, likely Montreal's oldest private historic museum, also briefly housed American revolutionary forces in 1775. Today, the museum's collection is composed mainly of gifts from private Montrealers and is estimated at 30,000 objects, including manuscripts, printed works, numismatic items, ethnological items, works of art, paintings, prints and furniture.

All museum visits begin at the Emmaus after the morning service, when the day's group forms and heads out together.