My property has about 1 mile of stone border walls around 3' tall, 2' wide, and in the corners giant piles of rocks, most in the 12-18" range, but some 4' - 5'. I know they pulled them all out of my property so they could farm, but in the 200 years since they were built more have grown. This property is on the southern side, just below the mountain peak (1600') so the glaciers scrapped across the top of the mountain and dropped the debris in the low spot it came to .. my place. My neighbor across the road to the north has no loose rock, but several areas of bedrock showing through the grass, most with nice north/south striations carved in them. I've dug up some big ones, my limit is about 275 gallon oil tank size ... and I'll typically have to roll that where I want it. There is also a nice 200 year old dry laid stone bridge across a creek that bisects the property .. very strong and stable and has withstood 200 years of floods that sometimes go right over the top of it.