Wow. Fantastic job at picking up all that trash you found, and disposing of it. Your efforts will certainly improve the value and long term enjoyment of your new property. I think the previous owners were simply not good caretakers of their property.
Unfortunately this type of trash disposal was more common than we think. Some badly misguided landowners many decades ago, often would charge a small dumping fee to allow disposal on their property. I am sure they made a few thousand dollars over the life of their property ownership. The other case, is you have a landowner, that lived remote to the property, rarely visited the property and did not maintain fencing to keep out locals from dumping. And that seems to be what happened to my property. Remote ownership.
In my particular property case, the trash we picked up from our heavily wooded property was dated back to years 1930 - 1970s, and so far we have moved a total of twenty three - 15yard dumpsters out to the county landfill. The landfill does not allow tires, refrigerators and toxic chemicals, and happily we had none of these type of trash. We have cleaned enough up, that last week, we actually hired a land clearing contractor, who uses a skid steer with forestry mulcher. He opened up paths through the woods, and found enough debris to fill another dumpster in just 3 days. I estimate we have 95% cleaned up, with some small areas avoided due to some rather steep terrain for tractor access.
