What document was the first written plan of government for the new nation for new nation of Canada who wrote it?

The first written plan of government for the new nation of Canada was the British North America Act of 1867, also known as the Constitution Act, 1867. It was drafted by British politicians, notably John A. Macdonald and George-Étienne Cartier, and it established the framework for Canada's federal government. This act united the provinces of Ontario, Quebec, New Brunswick, and Nova Scotia into the Dominion of Canada. It laid the foundation for Canada's political structure and governance.