My grandfather built a road on the side of his property in 1960 to access another parcel of land. I purchased this parcel in 1975. I built a house and then sold it in 2000. My grandfather now has past away and the new owners are rejecting access by closing the road. This road has been open and maintained by me for 25 years this cannot be possible? This property is located in oregon without an easement.

1) check on adverse possession law in oregon; often if boundaries or property usage can be established for a certain period of time prescribed by law, then you can make a claim and file to get a deed for it in court; this applies to property and usually easements
2) apply to the court for an easement by necessity since it is needed to access the road and had been used for that purpose for many years

That's the first thing that I thought of as well. I've heard 20 years is kinda of a standard in some states. Not sure about Oregon.