Pearson was very instrumental in establishing the worlds first ever peace keeping force at the UN General Assembly set up to watch over the Suez Crisis (was not yet a pm at this time but a foreign minister)
He set the framework for bilingualism and biculturalism that would follow through to when Trudeau entrenched what we have today
Introduced Canada Pension plan and Medicare as well as the Maple Leaf flag after many controversies in 1965
Diefenbaker is regarded for his appointment of the first female minister in Canadian history to his cabinet as well as first aboriginal member of his senate
He gave aboriginals and Inuit people the right to vote
Also under his rule he obtained passage of the Canadian Bill of Rights, this was the earliest expression of human rights law at the federal level in Canada
He established the official languages act in 1969 as well as the Charter of Rights and Freedom into Canadas constitution
Trudeau mande cuts on Canadian income taxes, and bettered the life of the poor and elderly
These Prime Ministers had all had a significant influence on the way Canada is goverened. Not all four of them had the same political standing, either liberal or a conservative they had each their own ideas and ways of running this country and as far as we see it, it was good enough to get Canada through tough times.