The history of the poutine is controversial to say the least. Many different people claim to have invented the poutine,
the only problem is that most of these claims aren't talking about he same poutine we know today.
The very first supposed "inventor" of the poutine was Fernand Lachance who mixed a plate of cheese curds and fries for a client who requested it. So this is technically the birth of the poutine, except it did not have any gravy.
Some say it was invented in either Nicolet or Saint-Hyacinth because of all the cheese curd producers in the region. And a third claim states that a restaurant in Princeville called La P’tite Vache invented the poutine. They sold bags of cheese curds at their counter and patrons began mixing them with their fries. The restaurant began selling it on their menu and had a variety that came with gravy on top which they called it "Mixte".
Photo cred - tripadvisor
But the first ever restaurant to serve poutine as we know it today was A Drummondville restaurant called Le Roy Jucep in 1964. They also have the first official trademark registration for a poutine naming the restaurant Le Roy Jucep as the official inventor.
This restaurant is still open today. It is located at 1050, Saint-Joseph Boulevard in Drummondville and it is technically the first restaurant to officially serve poutine. Though I'm sure the debate will never truly be settled.