Who was the Prime Minister of Canada in 1920?

Several (a decade is a long time in politics); counting downward:

• William Lyon Mackenzie King (1926 to 1930)
• Arthur Meighen (1926)
• William Lyon Mackenzie King (1921 to 1926)
• Arthur Meighen (1920 to 1921)
• Sir Robert Borden (1911 to 1920)