William IV, the third son of George III, became the first member of the royal family to visit Canada. He came in 1786, at the age of 21, while serving as a captain in the Royal Navy. In 1830, he succeeded his brother, George IV. His reign was marked by a fundamental change of the electoral system in Great Britain, when the Great Reform Act, 1832, extended the right to vote to a substantial portion of the middle classes landowners.

This reform had a decisive influence on Canada's political evolution. Rebellion broke out in 1837, led in Upper Canada by William Lyon Mackenzie, and in Lower Canada by Louis-Joseph Papineau. Both these popular movements sought to free the Houses of Assembly from the grip of the Governor and his councillors, and to take real control of the government and of the management of public funds for the benefit of the people. The British army had to intervene in order to restore order. The Constitution was suspended and the leaders of the rebellion found refuge and support in the United States.