In 31 years of paddling Quetico I have not once checked in at US customs in Ely or Grand Marais.  Until this year.  With unmanned drones watching the border for the hordes of illegal immigrants and drug smugglers paddling across the border, I won't be taking any chances!   ;D

That being said, I guided long canoe trips for a camp in eastern Ontario for a few summers while I was in college, and went through car searches, interviews, etc, on both sides of the border.  >:(