Top: map of the 860 km border between Chile and Bolivia Top Middle: border between Bolivia and Chile border Bottom middle: imigration office at the border Bottom: Bolivia and Chile border along the rail line.
A slightly old article about a different US-Canada border: the one between Canada and Alaska. It's relatively autonomous for people... but totally free for salmon. And it's causing this US official to freak out. After all, they should still be kept separate...