Speculative Freemasonry - the philosophical and ritual form that emerged from the medieval stonemasons' guilds - reached Canterbury in 1730. The city's first lodge began meeting at the Red Lion Tavern beside the old Guildhall on the High Street. According to Lane's Masonic Records of 1717 to 1894, three private lodges and six military lodges were eventually consecrated in the city. The lodges met for a century and a half in various pubs - the King's Head, the Brewers Arms, others - until 1878, when they pooled resources and bought premises at 38 St Peter's Street near the Westgate Towers. In 1880 they built a Masonic temple in the garden of that building. The accumulated regalia, paintings, manuscripts, and ceremonial objects of generations of Kentish lodges began piling up in the temple's lodge of instruction room, until space became a problem they could no longer ignore.

In 1919 the East Kent Masters Lodge No. 3931 was consecrated in Canterbury, and its first Master was Wykeham Stanley Cornwallis, 2nd Baron Cornwallis - the Provincial Grand Master of Kent. Looking at the growing collection, he conceived a Kent Provincial Library and Museum. Maidstone, the county town and provincial headquarters, was considered. So was Bromley, with its concentration of lodges. Cornwallis chose Canterbury anyway. An appeal was launched in 1920 under the chairmanship of W H East of Dover, with H C Page as secretary and H Biggleston as treasurer, both of Canterbury. Lodges across Kent donated. By 1925 the Province had paid 1,036 pounds 4 shillings 11 pence to Edward Dean of St Augustine's Lodge No. 972 for the garden of 34 St Peter's Street, where the new building would rise.

F G Haywood, a Dover architect and Mason, drew up the plans in 1930. W W Martin of Ramsgate and G H Denne and Son of Walmer built it. Meanwhile Cornwallis - by then also Deputy Grand Master of the United Grand Lodge of England - was watching the demolition of the old Grand Library and Museum in Great Queen Street, London. The site was being cleared for the new Grand Temple and Connaught Rooms. Cornwallis acquired the unique 19th-century stained glass windows from the old building, plus the internal doors and most of the display cases, and shipped them to Canterbury. A Worshipful Brother named Jimmy Edwards donated the solid oak entrance doors, salvaged from St Mary's College - the Jesuit house at Hales Place in Canterbury - which happened to be coming down at the same moment. The building cost 3,936 pounds 4 shillings 11 pence including the land. It was completed in June 1932 and officially opened by Lord Cornwallis on 19 April 1933.

The collection holds more than 3,000 pieces: Masonic paintings, manuscripts, regalia, ceremonial glassware, porcelain, books, and presentation items spanning every Masonic order through the ages. There are items linked specifically to Canterbury and Kent - documents tracing the founding of individual lodges, presentation jewels given to past masters, ceremonial aprons worn by men whose grandchildren may be the visitors today. The museum tells the history of Freemasonry from its disputed origins, through the formation of the first Grand Lodge in London in 1717, to the modern day. There are displays on famous Kent Masons and on Masonic military heroes. The walk-through layout was created during an extensive redevelopment that closed the museum in early 2011 and reopened it in September 2012, in a format designed to make Freemasonry's history legible to non-Masons.

Although the building sits in territory administered by the Masonic Province of East Kent, the museum itself is a Charitable Incorporated Organisation - charity number 1163887 - managed by a separate trust. Admission is free, the museum is open from 10 in the morning to 4 in the afternoon almost every day of the year, and wheelchair access is available throughout. It sits midway between Canterbury East and Canterbury West railway stations, a five-minute walk from the cathedral and close to the Westgate Towers. For visitors curious about the rituals and symbols Freemasonry has accumulated over its three centuries of formal existence, it is one of the few places in Britain where the doors really are open and the lights really are on. The 19th-century stained glass that once filtered the light over the Masons of London's Great Queen Street now does the same job over visitors in Canterbury - quiet, slightly mysterious, and surprisingly beautiful.