For a fee of C$25,000, César Ritz agreed to lend his name, but stipulated that by the "Ritz standards," every room was to have its own bathroom, there was to be a kitchen on every floor so room-service meals could be served course by course, and around-the-clock valet and concierge service were to be made available to the guests for, amongst other duties, tracking lost luggage or ordering theatre tickets.

[2] Finally, the lobby was to be small and intimate, with a curved grand staircase for ladies to show off their ball gowns on their descent.

Its doors officially opened at 11:15 pm on New Year's Eve, 1912, marked by a gala ball attended by 350 guests.

[7] In 1918, Lord Birkenhead described the hotel as "very luxurious and comfortable,"[8] and the American Bankers Association held its annual meetings there.

In 1929, he lamented that before, guests had come to stay for several weeks accompanied by trains of luggage, but during this time, when they did come, they came for a night or two with only a single bag.

In the 1930s, when the widows and residents of the Golden Square Mile began to downsize from their mansions, many prominent people took rooms in the hotel, such as Lady Shaughnessy and founder Charles Hosmer's son, Elwood, who, between him and his sister, had inherited $20 million from their father in 1927.

[9] The hotel had guests such as Winston Churchill, Charles de Gaulle, Marlene Dietrich, Liberace, Tyrone Power and Maurice Chevalier.

He opened Le Bar Maritime in 1948 and in the early 1950s, added the Ritz Garden, where patrons could dine around a flower-fringed pond, which was home to twenty-four ducklings.

[12] In 1957, a new wing consisting of sixty-seven rooms and suites was added, and care was taken to maintain the original Ritz-influenced Louis XVI and Carlton-influenced Regency styles and ambiance.

[3] In 1971, Richard Nixon stayed there, and in 1972, The Rolling Stones booked out the entire sixth floor, but were refused service in the main dining room for not being suitably attired; they later returned in jackets.

In 1977, champagne corks were popped at the Oval Room party, at which 600 guests bade farewell to esteemed General Manager Fred Laubi while welcoming his successor.

The same year, in order to celebrate the Dames and Messieurs of the Ritz-Carlton, all the employees and their spouses were invited to dine at the Café de Paris.

Other leading figures of the 20th century that stayed at the Ritz-Carlton Montreal include Charles de Gaulle, George H. W. Bush, and Céline Dion.