I grew up in the Boston area around the same time. Another factor that limited interest in flying to sunny beach places was we already had options close to home during the warmer months, such as Cape Cod, Cape Ann, Hull, Rhode Island, Southern Maine, and so on. Lots of people including families of modest means had cabins in these areas. For the winter months, there were two "sun" locations that weren't too far away:…
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I agree with you about the Maritimes. The bridge has made a difference but it's still a long drive and as you noted there are few famous destination cities or attractions.
Regarding Quebec: It seems that far more Quebeckers are aware of New England attractions in Boston and points north than the other way around. You see them or hear them at ski slopes, beaches, concerts in Boston, etc. Yet few New Englanders have been to Montreal, and even fewer have even heard of Quebec City, the walled European city and heritage site just a few hours downriver.