The Dominion of Canada formed in 1867, but as an integral part of the British Empire its foreign relations remained under the control of London. Over the next six decades Canada gradually won greater control over its external affairs, spurred in part by the demands of managing its relationship with the United States. American and Canadian government officials increasingly interacted through joint commissions and military cooperation, and the two governments even negotiated a bilateral fisheries treaty in 1923. It was not until 1926, however, that the United Kingdom acknowledged that Canada was fully autonomous in the conduct of its foreign affairs.Modern Flag of Canada
The United States recognized Canada as an independent state with autonomous control over its foreign relations on February 18, 1927, when Vincent Massey presented his credentials in Washington as Canadian Envoy Extraordinary and Minister Plenipotentiary. This action followed the 1926 British Imperial Conference that produced the Balfour Declaration, which stated the United Kingdom and the Dominions
“are autonomous Communities within the British Empire, equal in status, in no way subordinate one to another in any aspect of their domestic or external affairs.”
Diplomatic relations were established on February 18, 1927, when Vincent Massey presented his credentials in Washington as Canadian Envoy Extraordinary and Minister Plenipotentiary.
The American Legation in Ottawa was established on June 1, 1927, when William Phillips presented his credentials as Envoy Extraordinary and Minister Plenipotentiary.
The American Legation in Ottawa was elevated to Embassy status on November 19, 1943, when Ray Atherton presented his credentials as Ambassador Extraordinary and Plenipotentiary.