I'm trying to save money. Raw clay isn't super expensive, but if you want a lot of it, it adds up. And I am trying to provide enough for not just me but some friends. Maybe 20-30 lbs of it.

Most dirt has some clay in it. Clay is just mineral deposits composed of particles smaller than silt. And it tends to get filtered by water and deposited in pools and the like. It can usually be found in stream beds, but around here that would mean digging through riparian roots and stuff and standing in water. 

But another good place to find it is an old dirt road, dirt (not grass) parking lots, or old dirt piles. But it has to be pubic, not private. I don't want to be stealing anyone's land (literally). Construction sites would likely have it, but they usually don't want anyone climbing over the dirt piles and will be strictly no-trespassing. Ideally I'd want dirt that has a lot of clay in it (you can tell because it leaves well defined tire tracks when people drive through it, and it cracks as it dries out)

But there's not a lot of dirt roads in Boston proper. So I need to head outward a bit, preferably north if possible. The problem is I don't know where to look for 'em. And it doesn't seem to be something I can search for on google maps.

So, anyone know a spot?

This is kind of a weird question, but where can I find a public dirt road or lot so I can dig up some clay soil?