Here is the Roosevelt proclamation. It says the land can be only used for road construction and applied to California and the territories of AZ and NM.
https://en.wikisource.org/wiki/Proclamation_758
And yet, it is a presidential proclamation and thus subject to a presidential modification by another president.
Texas had and still has a Land Patent Law, so no easement from them was given to FDR from the state of Texas.
may be used for public highways but for no other purpose whatever,
Perhaps a really tall center median?