Standing on the USA/Canada border at an unmanned checkpoint near Angle Inlet, Minnesota.  This crossing is unique in that is the only place in the US outside of Alaska that passes above 49 degrees north latitude.  A small section of land 123 square miles in size (including outerlying islands) as well as 596.3 square miles of waterway is known as the Northwest Angle.  It is only accessible via going through Canada, unless you take a boat across Lake of the Woods from Minnesota proper.  A mapmaker's error from the 1783 Treaty of Paris had miscalculated the Mississippi River's source from Lake of the Woods, which had ultimately created the Northwest Angle as ownership of the United States & has been that way since.  The area houses a population of 119 people w/ limited services.

Seen here is the border w/ Minnesota & Manitoba.  A line through the forest is the boundary going north/south.  As you drive about eight miles in the US side, you have to stop at a road intersection called Jim's Corner where a single small unmanned booth is located, equipped with two telephones.  You use the videophone to dial customs, one either for US or Canada to declare your presence in either country.

More info at: 

https://en.wikipedia.org/wiki/Northwest_Angle