Amor De Cosmos was born William Alexander Smith in Windsor, Nova Scotia, to United Empire Loyalist parents.

The city, since 1843 a quiet village of about 300 until the spring of that year, was just entering an economic boom as it became a jumping-off point for miners headed to the New Caledonia (now mainland British Columbia) to participate in the Fraser Canyon Gold Rush.

[citation needed] De Cosmos was the editor of the Colonist through 1863, and quickly established himself as an opponent of the administration of Sir James Douglas, governor of the colony and the former Chief Factor of the Hudson's Bay Company for Vancouver Island.

He argued passionately for unrestricted free enterprise, public education, an end to economic and political privileges, and — above all — the institution of responsible government through an elected assembly.

He was a tireless advocate for economic diversification, being one of the first British Columbians to argue for a policy of encouraging development of the "three F's" — farming, forestry, and fisheries — that would underpin the region's economy for the next century.

To advance the first cause, De Cosmos left journalism and entered politics, becoming a member of the Legislative Assembly of Vancouver Island from 1863 until its union with the Colony of British Columbia in 1866.

He advanced the second cause through his position as a member of the assembly of the merged, larger British Columbia from 1867 to 1868 and 1870 to 1871, and as the leading force (with Robert Beaven and John Robson) behind the colony's Confederation League.

Despite his prominence — or perhaps because of it — Lieutenant Governor Sir Joseph Trutch passed over De Cosmos for the job of Premier,[citation needed] instead asking John Foster McCreight to assume the position.

Consistent with federal promises to place the terminus of the transcontinental railway in Victoria, De Cosmos, in Ottawa, pushed for completion, especially of the Vancouver Island portion.

De Cosmos also became an opponent of land concessions to First Nations in the province, seeing it as a hindrance to British Columbia's economic growth and settlement by those of European descent.

Although widely regarded as a stirring orator, a master debater, and a man of great intellectual depth, De Cosmos had always been considered eccentric.