Buying remote land or forestry. Unknown owner?

[Michael Ferguson]

Let's say I'm driving upon the highway and I see a nice plot of land that looks like a good spot to build a new home. How would I go about purchasing that plot of land? In most instances would that land be unavailable because it is next to the highway? Also, what would the case be for more remote plots of land, such as nice spot in the woods for a cabin?