Cow pastures. If you look at old photos you can see that Vermont was much less wooded and consisted of land that had been cleared for logging, for farms or for pastures. That is what supported the economy of Vermont at the time.
In the 80s and 90s I spent a lot of time clearing trees in Vermont... we actually used the same logging roads that survived (a bit overgrown!) from the early 1900s.
People love the changing trees in fall in Vermont, but in a lot of ways the open rolling hills that are much more rare now were very picturesque. "The Trouble with Harry" by Alfred Hitchcock (1955) was filmed in my great-great grandparents hometown of Craftsbury, Vermont. It gives a good idea of Vermont in the 20s to 50s. Newhart, on the other hand, shows Vermont as it was in the 80s, when the forests took over.