Almost due north of Minneapolis lies the border between the provinces of Ontario and Manitoba, where the Canadian west, with its great wheat-producing plains, oil fields, and about one-quarter of the country's 23 million people, begins.
Though Canada has no such thing as the Mason-Dixon line, the Ontario-Manitoba border is beginning to acquire a similar symbolic importance -- only here the division is not between north and south but between east and west.
Western alienation, a fact of life throughout the 113- year history of this 5 ,000-mile-wide country, reached new heights last week after an election that left the Canadian west with almost no voice in Parliament.
In Manitoba, Saskatchewan, Alberta, and British Columbia, the defeat of Progressive Conservative Prime Minister Joe Clark, the Albertan whose minority government was voted out after only nine months in office, was viewed as a major setback for the west's aspirations.
Shrill talk of secession, a word most often reserved for the country's other major regional sore point -- the Province of Quebec -- echoed from VAncouver, B.C., to Winnipeg, Manitoba, last Week.
It came in reaction to a massive sweep of votes in Canada's two most populous provinces, Ontario and Quebec, by the Liberal Party and Pierre Trudeau, who this week resumes an 11-year stint as prime minister, interrupted by nine months of Conservative rule.
Though Mr. Trudeau from the outset of the campaign spoke of broadening the Liberals' shrinking western base, this proved wishful thinking. Of the 146 House of Commons seats from the west, Mr. Trudeau captured only two in the Winnipeg area, the worst showing by his party in the region in two decades.
Few doubted that the majority government handed Mr. Trudeau as anything but an attempt by Ontario and Quebec voters, who now feel the west's soaring oil- based economic and political clout, to reassert central Canada's traditional sway over Canadian policies.
The message hardly went unnoticed in the west.
"East returns Trudeau Liberals to power" read the post-election headline in the Vancouver Province. On its editorial page, the paper added, "With these election results, Ontario has teamed up with Quebec in an assertion of central Canadian interest against those of the west."
This complaint runs deeply through Canadian history. Much of this century, westerners have contended that import-tariff and freight-rate policies wrought in Ottawa have favored the industrial east at the expense of western consumers and farmers.
As Canada's oil-producing region, the west hopes to use its burgeoning petroleum riches to build up its industries. Therefore, the region has long been angered by Ottawa's policy of keeping domestic oil prices well below world prices, which the Province of Alberta claims has amounted to a $15 billion subsidy from it coffers to the rest of Canada since 1974.
British Columbia Premier Bill Bennett, echoing other western leaders, said not long ago: "There is no reason why we should have to remain a colony of Canada and ship our resources east."
With the election last May of Mr. Clark, a former aide to Alberta Premier Peter Lougheed and an avowed champion of provincial rights, the west finally seemed about to get its long-desired hearing in Ottawa.
Indeed, Mr. Clark was true to his convictions, negotiating an agreement benefit to the western producing provinces, particularly Alberta, source of 85 percent of Canada's crude.
But those gains may be eroded now that Ontario voters, reacting against Mr. Clark's plans for higher fuel costs, have returned to office a Liberal Party committed to rolling back the high oil prices promised Alberta by the Conservatives.
With battle lines now so sharply etched, the prospect is for a major showdown between Mr. Trudeau and Mr. Lougheed, old arch-foes from previous energy-pricing wrangles.
And, though no one wants to be alarmist, something akin to sword rattling is under way already. Within days of the election, Mr. Lougheed stated that Mr. Trudeau's formula for oil price increases below those promised by Mr. Clark "is not workable and not acceptable."
Mr. Lougheed further hinted that if the coming negotiations with Ottawa become deadlocked, the province has "contingency plans" in mind, raising speculation across the country of a possible legal move by Alberta to cut off crude supplies to central Canada.
Such a move would bring on a confrontation sure to rival -- and possibly even dwarf -- the issue of Quebec independence, which took a back seat to energy questions in the election campaign just ended.
Any unilateral cutoff of supply by Alberta would cause Ottawa to assert control over the province's oil under special powers of the federal Constitution , probably leading to court challenges that would be a source of major uncertainty for years.