As I used Google Maps to calculate my 1973/74 long ski trip for that thread, I wondered what interstates were in use. I tried to find an article on such. I don’t think I’ll look more but I found “The East-West New England I-92”. There were (at least) three paths proposed. The article shows 3 maps. Below are selected paragraphs. I'm sure the Canadian government was interested in the northern route.
I-92
ANOTHER ATTEMPT AT AN INTERSTATE HIGHWAY DESIGNATION: In 1970, the states of New York, Vermont, New Hampshire, and Maine collaborated on two new proposed Interstate routes. The routes among a total of approximately 10,000 miles submitted under the guidelines of the 1968 Federal Highway Act, which called for a total of 1,500 new Interstate miles. They were routed as follows:
• 174.3 miles of new Interstate mileage from Albany, New York east to Portsmouth, New Hampshire. This highway would have incorporated the route of the current NH 101 Expressway (Exeter-Hampton Expressway).
• 388.2 miles of new Interstate mileage from Glens Falls, New York east to Calais, Maine. This amount does not include overlay mileage along I-89 and I-95, which would have been incorporated into the east-west highway.
In 1971, Bartlett Cram, industrial consultant; Hamilton South, a former Marine brigadier general who was Vice President of Albany's National Commercial Bank and Trust Company; and Clifford Barnes, executive vice president of the Rutland (Vermont) Chamber of Commerce, offered their own proposal: a 500-mile-long expressway (with approximately 367 miles of new construction) linking Amsterdam, New York with Calais, Maine. The transportation link was devised as an economic catalyst for the "Appalachia of New England." Like the official state submissions, this group also sought 90 percent Federal financing for the route.
MAINE OFFICIALS RESURRECT PLANS: More than a quarter century after I-92 was cancelled, officials in Maine and Canada devised plans for an east-west highway connecting the Maritime Provinces with Montreal, Quebec City and Toronto. The 1999 "East-West Highway Study" developed by the Maine Department of Transportation (MaineDOT) proposed five corridors -- three on existing alignment and two on new alignment -- all of which would be paid 80 percent by the Federal government:
http://www.bostonroads.com/roads/I-92/