[3] The reduced tariff led to increasingly profitable shipping through the St. Lawrence route.

Accordingly, a trade sprung up in American grain, shipped to Canada for milling, and then on to the UK.

[6] After a short time, the advantages to Canada of the Corn Act were undone when British Prime Minister Sir Robert Peel moved Britain towards free trade.

A shortage of food caused by the Great Famine of Ireland created the need for cheap imported grain,[7] and the act was repealed in 1846.

[8] This was seen at the time as blow to Canada by abolition of the (effective) imperial preference the act had created;[9] the impact of the repeal to grain exports in practice, in the later 1840s and 1850s,[8] remains a subject of historical debate.