It's at Grand Forks AFB, for "Special Security reasons", and says:
"EXCEPT AS SPECIFIED BELOW AND/OR UNLESS AUTHORIZED BY ATC:
ALL AIRCRAFT ENTERING OR EXITING THE TFR MUST BE ON A DISCRETE CODE ASSIGNED BY AN AIR TRAFFIC CONTROL (ATC) FACILITY.
AIRCRAFT MUST BE SQUAWKING THE DISCRETE CODE AT ALL TIMES WHILE IN THE TFR.
ALL AIRCRAFT ENTERING OR EXITING THE TFR MUST REMAIN IN TWO-WAY RADIO COMMUNICATIONS WITH ATC.
MINNEAPOLIS CENTER, PHONE 651-463-5580, IS THE FAA COORDINATION FACILITY."
I'm betting it's a path to and from Class A for UAV ops.