Reciprocity was a free trade agreement between the United States and Canada. It mutually reduced import duties and protective tariffs on certain goods exchanged between the two countries. It was in effect from 1854 to 1866 and was controversial at times on both sides of the border. It was replaced in 1878 by the Conservative Party’s protectionist National Policy. It involved levying tariffs on imported goods to shield Canadian manufacturers from American competition. A narrower reciprocity agreement was introduced in 1935 and expanded in 1938. However, it was suspended in 1948 after both countries signed the General Agreement on Tariffs and Trade (GATT).