The Senate of Canada had 72 seats when Confederation began in 1867.
The original Senate was divided into three regional groupings rather than allocated simply by population. Ontario had 24 seats, Quebec had 24, and the Maritime division had 24 more: 12 for New Brunswick and 12 for Nova Scotia. This arrangement reflected the Confederation bargain and gave the regions a strong voice in the appointed upper chamber.
The Senate was created by the British North America Act, 1867, now called the Constitution Act, 1867. Its members were appointed, not elected. The first Senate therefore differed from today’s chamber both in size and in its provincial distribution. As new provinces and territories joined Canada, additional seats were added. The normal total eventually rose to 105, the number many readers recognize today; that is why 105 is a tempting but incorrect answer for the Confederation-era question. The first Parliament’s 72 senators were named in the proclamation of Confederation.