The Medicine Line is the US/Canadian Border. Specifically, the part of the border that runs along the 49th Parallel from the Midwest to the Pacific Ocean. In the frontier days when battles between US troops and Native Americans were common, the tribes would often flee North into British/Canadian territory to rest and recuperate after a fight. Because the land North of the 49th Parallel was not American territory, US soldiers were forced to stop at that point, and allow the tribes to get away. For it's apparently magical ability to stop advancing American troops, Native Americans gave the 49th Parallel the name "Medicine Line," a term that shows how tribes at that time believed medicine and magic to be closely connected.

The term is still used extensively in Western North America, especially by people who cross the border frequently.
"Are you driving from Seattle to Vancouver today?"

"Yep, I'm crossing the Medicine Line."
by KBLI October 30, 2009
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