That made me curious so I looked up the act referenced in the extension letter (50 U.S.C. 1622(d)). There was no real mention of anything but declaration and termination of National Emergencies, so I went up a level. There in Title 50, you find chapters about Alien Enemies, Espionage, Atomic Weapons, Insurrection, Defense Against Weapons of Mass Destruction, etc.
So from what I can tell, the government sold some land to the girl scouts for $1 in exchange for the right to build a helium pipeline. They surveyed it by putting an X on a rock and guessing at the size of it, more or less.
The National Emergency is probably similar - the government bought or sold something, someone signed with an X, and they agreed to blow things up and kill people until whenever, more or less.
