What does the national motto 'A Mari Usque Ad Mare' mean?

A Mari Usque Ad Mare is Latin for 'From Sea to Sea', and is Canada's national motto. It was proposed by Sir Joseph Pope, the federal Under-Secretary of State, drawing on verse 8 of Psalm 72: 'He shall have dominion also from sea to sea, and from the river unto the ends of the earth.' King George V granted the motto by royal proclamation on November 21, 1921, the same day he proclaimed Canada's red and white national colours and approved the Canadian coat of arms.

The phrase originally referred to Canada's reach from the Atlantic to the Pacific, but the country also fronts the Arctic Ocean, and contemporary expressions sometimes extend the motto to 'A Mari Ad Mare Ad Mare' or 'From Sea to Sea to Sea' to acknowledge the three coastlines. The shorter Latin phrase remains the official version on the Royal Arms of Canada.

The motto appears on the lower scroll of the Canadian coat of arms, beneath the shield, the lion holding the Royal Union Flag, and the unicorn holding the Royal Banner of France. It is engraved on the Mace of the House of Commons, on diplomatic credentials, on Canadian military badges, and on the Centennial Flame on Parliament Hill, lit on January 1, 1967 to mark Canada's hundredth birthday.

A Mari Usque Ad Mare captures the geographic ambition of Confederation: the 1867 Constitution Act bound three eastern colonies into a transcontinental project that was completed when British Columbia joined in 1871, Prince Edward Island in 1873, and the Canadian Pacific Railway drove its last spike in 1885. The motto remains a shorthand for that national-scale ambition.