Many schoolbooks in Canada will tell you that after Upper and Lower Canada were joined in 1841, the Governor appointed two men to serve jointly as premier of the United Province of Canada. Although that had some practical truth to it, it was, indeed, a lie. The Governor appointed a Premier and a Deputy Premier.
But almost straight from the beginning, the Governor recognized the need for representative balance, and every ministry from 12 January 1842 onward consisted of one of the two being from Canada West and the other from Canada East; and although the Premier had the power to do as he saw fit, the politics of the Canadas were such that he dare not do anything without the fullest support from his deputy.
The choices for Premier and Deputy Premier were made by the Governor until the introduction of responsible government under Gov. the Rt. Hon. the 8th Earl of Elgin & 12th Earl of Kincardine in 1848, with Sir Louis-Hippolyte LaFontaine as Premier and Robert Baldwin as Deputy Premier.
When Premier Sir Francis Hincks was forced to resign over a railway scandal in 1854, the Clear Grit Party (our modern Liberals) were formed in Canada West, there by establishing matching conservative and liberal parties in Canada West and Canada East. Thereafter, each set of Premier and Deputy Premier would belong to matching parties, either the Clear Grits and the Parti rouge, or the Liberal-Conservative Party and the Parti bleu.