Established in late 1926, the northern terminus of US 97 is at the US-Canada border between Oroville WA and Osoyoos BC. In 1953 British Columbia changed some of their route designations, including BC 97, which now begins at the same border crossing as US 97 and continues all the way up to the boundary of the Yukon Territory. In 1959 Alaska became one of the United States, and in 1964 the recently-formed Alaska Dept. of Highways sent an application to AASHO requesting the US 97 designation in their state. Why would Alaska want a US route? They anticipated and answered that question in their application; following is an excerpt:
AASHO's response was generally favorable, although tempered by the stipulation that Alaska could signpost its portion of the route as US 97 only if both BC and Yukon also designated their segments of the Alaska Highway with the number 97. Since BC had already done this, AASHO was really referring to the Yukon:
When viewed as a combined unit, the proposed bi-national Highway 97 Corridor would have been quite substantial: nearly 2900 miles in length, as shown on this map:
Yukon Territory assigned numbers to its highways in 1968, but unfortunately they opted not to designate their segment of the Alaska Highway as Yukon 97 (instead they christened it Yukon Highway 1). Later that year, AASHO exchanged correspondence with Alaska Dept. of Highways, whose response included this paragraph:
In my opinion, AASHO should have allowed Alaska to use the US 97 designation regardless whether or not Yukon went along with the idea. But even though AASHO did not, Alaska still could have re-numbered their segment of the route as Alaska 97. Either scenario would have created the appearance that Yukon was the only uncooperative entity in the group, which may have eventually caused them to change their position on the issue.