Under the charter, French was to become the official language of business, as well as the government, the courts and commerce.
Immigrants would only be able to school their children in French, including out-of-province Canadians moving to Quebec.
Former PQ premier Bernard Landry says the new atmosphere Bill 101 created was good for both the French speaking and English speaking communities as well as for immigrants who spoke a different language altogether.
READ MORE: What is Bill 101?
He says the bill leaves behind a great legacy, noting that before, practically all the children of immigrants went to English school, which was bad for them and bad for Quebec society.
In Montreal, Quebec flags could be seen in abundance at the Camille Laurin monument as supporters gathered Saturday in celebration of the legislation’s 40th anniversary.
“It’s been an integrating law rather than a dividing law,” Jean-François Lisée, Parti Québécois leader, said.
Robert Libman, a leading anglophone-rights advocate in the 80s and 90s, says at the time, the legislation jolted the anglophone community.
WATCH BELOW: Language debate in Quebec
He says it dramatically altered the psyche of the anglophone community, which had never before seen itself as a minority.
READ MORE: Quebec’s Bill 101 language law turns 40
Libman says today’s anglophones are more bilingual, but the community has been decimated.
In 1971 there were 250-thousand children in English schools across the province, while today there are fewer than half that.