Where i'm located most town halls are very new. The one in my town is maybe 10 years old. The previous one was actually a shared building with the library, which had no lawn. We only have one old park in the area (1870's or so), and that's the one they decided to tear up and build the new seperated library and town hall on. Go figure.
I only know of one other old town hall in the area, and of course it's the one town that strictly bans detecting.