We have lots of public land sitting behind private land with no access other than climbing over a mountain range. If you can get to it, it's open to the public but unless the landowner cooperates, you can't cross his land to get to it. When the land was settled, settlers staked claims on much of the land with good water and flat land for farming. The steep stuff behind it wasn't claimed. Many large ranches were able to get possession of small parcels that controlled the water so the surrounding land can't be used for grazing because there's no water. That gave them sort of a defacto ownership. They don't own it but you can't get to it.
Some ranches would have their workers homestead on strategic parcels with water. As soon as they proved up and got title, they turned it over to the ranches. That wasn't exactly legal but it happened over and over across the west.
