Mackenzie knew the value of good relations with the First Nations people.  He employed Chipewyan men as guides on his expeditions.  He was also guided by Aboriginal people along the Fraser river when he reached what is now B.C.  They offered to show him the way to the ocean along what they called the "grease trail".  This was the trail used by Aboriginal people to trade between different groups. A main item of trade was the oil from the eulachon fish, since this was a delicacy.  This is why it was called the "grease trail", because of the fish oil trade.

Without his First Nations guides, Alexander Mackenzie probably would not have found his route to the Pacific.