PS: I'm disappointed to hear you only saw a few farmers markets on the TA! They seem to be everywhere where I live but I guess this part of the country is also a little more environmentally friendly than the rest or at least they make that claim!
I think it has more to do with the roads you're route takes you on than how "environmentally friendly" the area is. Farmers around here will drive 15 miles to put up a stand on the side of a U.S. highway, for instance. Those are the high-speed, heavily traveled highways I do my best to avoid on a bike. The old highway is now a state or county route, perfectly fine for cycling, but I haven't seen any farm stands on it.
Markets with multiple farmers tend to be either (a) local farmers bring produce to market one or two days a week, probably not the days you pass through town according to Murphy's law; or (b) dominated by commercial outfits trucking produce in from hundreds of miles away, but they're open six or seven days a week.