The Permanent Resident Card (PR Card) was introduced on 28 June 2002 upon the implementation of Canada's Immigration and Refugee Protection Act

Immigration and Refugee Protection Act

Immigration and Refugee Protection Act is an Act of the Parliament of Canada, passed in 2001 as Bill C-11, which replaced the Immigration Act of 1976 as the primary federal legislation regulating Immigration to Canada....

. It was originally billed as the Maple Leaf Card

It is the primary method by which Canadian permanent residents

Permanent resident (Canada)

A Permanent Resident in Canada is someone who is not a Canadian citizen but who has been granted permission to live and work in Canada without any time limit on his or her stay...

 (formerly known as landed immigrants) can prove their status and is the only document that allows permanent residents to return to Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. However, those from nations not requiring a visa to travel to Canada may be allowed entry on the strength of their passports alone.
It is necessary to supply a Canadian residential address at the time of landing.