Which treaty helped open up restrictive trading policies during the Depression era?

The General Agreement on Tariffs and Trade (GATT) opened up the world's restrictive trading policies that had developed during the Great Depression. According to Discover Canada: "The world's restrictive trading policies in the Depression era were opened up by such treaties as the General Agreement on Tariffs and Trade (GATT), now the World Trade Organization (WTO)."

The Great Depression — also called "the Dirty Thirties" in Discover Canada — devastated economies worldwide and led many countries to raise tariffs and restrict imports as a form of protection. After World War II, GATT was created to reverse this trend and re-establish global trade.

The post-war era brought rapid prosperity to Canada. Discover Canada notes that the discovery of oil in Alberta in 1947 began Canada's modern energy industry, and that by 1951, for the first time, a majority of Canadians were able to afford adequate food, shelter and clothing.

Between 1945 and 1970, as Canada drew closer to the United States and other trading partners, the country enjoyed one of the strongest economies among industrialized nations. Today, Canadians enjoy one of the world's highest standards of living, "maintained by the hard work of Canadians and by trade with other nations, in particular the United States."

GATT eventually became the World Trade Organization (WTO). Later, Canada joined the broader North American Free Trade Agreement (NAFTA), which Discover Canada describes as covering over 444 million people and over $1 trillion in trade.