Sarah Trumble and Nathan Kasai for Third Way: Only one-third of the land on which the southern border is located is owned by the federal government or Native American tribes. The rest is largely state property or farmland owned by individual ranchers.

Sixty-six percent of the total land on the border is owned by states or individuals, most of which is along the Rio Grande River in Texas. That means to build any structures there, the federal government must receive permission from each individual landowner whose property will be affected or must exercise its powers of eminent domain to take possession of the land.