Following the union of Upper and Lower Canada in 1841, Kingston was chosen as the capital of the United Province. The new municipal hospital was hurriedly modified to provide temporary legislative chambers and here the three sessions of the first Parliament were held between June 1841 and December 1843. Political pressures and inadequate accommodations led to the decision in 1843 to transfer the seat of Government to Montreal, where the second Parliament met for the first time in November 1844.

After rioters burned the legislative building at Montréal in 1849 during the Tory protest over the Rebellion Losses Bill, the seat of the provincial government alternated between Toronto and Québec. The sessions of 1850, 1851, and 1856 to 1859 were held in buildings originally erected (1829-1832) for the Legislature of Upper Canada in York, later Toronto. These buildings, which occupied the block bounded by Wellington, Simcoe, Front and John Streets were demolished in 1904.

Between 1850 and 1866, the Capital of the Province of Canada alternated between Toronto and Québec. In 1852, Parliament met in the Legislative Chambers of Lower Canada on the site of the old Bishop's Palace, now Montmorency Park. When these buildings burnt in 1854, the legislators took up temporary quarters in the Music Hall on St. Louis Street until 1856. Pending the completion of the Parliament Buildings in Ottawa, sessions were held in newly built quarters in Montmorency Park. This building, the site of the 1864 Québec Conference, was the Québec legislative building from 1867 until burnt in 1883.

In 1841, Britain created the Province of Canada, bringing together Upper and Lower Canada, following the 1837–1838 uprisings. The legislature first met in Kingston before political pressure forced a move to Montréal in 1844. Equal parliamentary seats in the legislature disadvantaged the French-speaking majority of Lower Canada and subsequently the growing English-speaking population of Upper Canada. In 1849, English-speaking protestors burned St. Anne’s Market, the seat of Parliament. Ongoing unrest led the legislature to alternate between Toronto and Québec City until Ottawa became the capital in 1866.