In that year [1871] British Columbia decided to become part of theDominion of Canada, on condition that a transcontinental railway should be completed without delay.
2001, Alan Rayburn, “Looking at Canada's Places from the Atlantic to the Pacific, and to the Arctic”, inNaming Canada: Stories about Canadian Place Names (nonfiction),University of Toronto Press,→ISBN, How Canada Lost Its 'Dominion',pages17–18:
About that time, I was asked by the United Nations to confirm the official long and short names of our country. I assumed the long title wasDominion of Canada, and the short was simply Canada. I was wrong. External Affairs declared that Canada alone was official as both the long and the short name.[…] Historians trace the origin of the titleDominion of Canada in the constitution to SirSamuel Leonard Tilley, one of the Fathers of Confederation, from New Brunswick.
Name of Canada on Wikipedia.Wikipedia