See also the chapter on prime minister biographies.
In the first 90 years following Confederation, Canada technically had no formal office of prime minister. The highest institution in the executive branch was simply the cabinet, and whichever cabinet minister was leader of the ruling party was called head of cabinet or head of government, and informally referred to as Canada’s prime minister or premier. It was not until 1957 that someone served as prime minister without also holding another cabinet job. Likewise, prior to 1957 there was no inauguration for prime minister; record keepers simply consider a pre-1957 prime minister’s term to have begun when he was sworn into the cabinet job he got when his party assumed power.