It was also the attempted entry point for a vehicle full of explosives just prior to the 1999/2000 New Years events.
Canada is known to have numerous Muslim population centers, including several large, long established and well organized Islamic extremists centers. Two of the largest are in Vancouver, BC and near Windsor, ON where they can interact with the Muslims in Dearborn, MI (the largest Muslim population center in the U.S.).
Border patrol agents on the southern border have long out numbered those on the northern border by about 8 to 1 (even though the northern border is vastly larger, has hugh stretches of lightly populated areas, is hardly patrolled and wide open in many places for miles and miles). In August, in recognition of the growing recognition of the real threat our northern border offers, customs announced it was going to shift a lot of agents to the Canadian border.
You can worry about the Mexican border all you want, but it is far more secure than our northern border which is known to be a major point of entry for terrorists. And while you're busy putting the military on the Mexican border the terrorists are boating tons of weapons across Lake Erie, or skimming across the Detroit River in two minutes with a load of explosives, or driving a Jeep full of anthrax into North Dakota, or bringing in more fishing trawler full of terrorists down along the northeast coast, or....or a few thousands miles of endless possibilities.
You folks are putting dead bolts and armed guards on the front door and the whole time they're coming in and out of the back of the house...where there aren't even any walls.
Er, didn't they enter the US legally and overstay their visas? Facts, please.