Very interesting! Here's the text of the postcard in case it is hard to read:
"One of the most asked questions of the Maine tourist has to do with the term "Down East." It would seem that inasmuch as Maine is north of the rest of the country, "down" is a contradiction of terms. In early times, it turns out, the state was generally reached from Boston and other points by sailing vessel. Since the prevailing wind is westerly, travelers sailed down wind to Maine, creating the local term, "going down to Maine" or "down east".
Received May 16, 2011.