The British Preferential System

Until the 1840s, the British government gave tariff protection to products imported from its colonies, whether from North America or elsewhere. When London decided to phase out this protection and to adopt a free trade policy, the high price of Canadian products made it hard to find buyers in the international markets.

The Canadian economy changed substantially when the British Corn Laws were repealed in 1846, followed by the gradual repeals of the Canada Corn Act in 1849 and the preferential tariffs on timber in 1847 and 1848. Canada had depended mainly on British preferential tariffs until that time.

It was during this time that Canada began turning to the United States as its commercial partner. This trend would lead to the Reciprocity Treaty in 1855.

Source

Careless, J. M. S. -- The Union of the Canadas : the growth of Canadian institutions, 1841-1857. -- Toronto : McClelland & Stewart, 1967. -- P. 109-112.