The line was invisible on the land.

But it carried specific and significant meaning.

American soldiers could not legally pursue Indigenous people across it.

The authority of the United States Army stopped at the border.

Canada had different laws and different relationships with Indigenous people — not necessarily better ones, but different ones, governed by different institutions and operating under different rules.

For Sitting Bull and his Lakota followers, who had crossed the Medicine Line in 1876 after the Little Bighorn, the border had provided a specific kind of sanctuary.

The North-West Mounted Police — the Mounties — administered the Canadian territories with far fewer personnel than the American army deployed, and their approach to the Lakota refugees had been different from the American approach: negotiating, establishing relationships, enforcing Canadian law without the scale of military force that characterized American Indian policy.