Hudson's Bay Company blankets got a mention in the Alden Amos book. The blankets are one of those things that if you grow up Canadian you don't really think about: they are just there. So I thought I'd go to the source and learn a bit more about them.
The Bay's site has information on the blanket's history here and faq here including information on dyes (like indigo) and the source of the wool (Britain and New Zealand).
The Bay is a major department store in Canada. They've sold Hudson's Bay blankets continuously since 1668. Hudson Bay is the big dip you see on the map in Northern Canada. Back in the 1600s, the Crown (the government of England) gave the Hudson's Bay Company a Royal Charter so they could trade for furs with the indigenous people. The company's activities had a significant impact on the development of our country.
HBC set up forts all over, not just Hudson Bay. There was one in Victoria, British Columbia; the former outline is marked in special bricks along Government street and Bastion square is named for the fort's tower. There's a bastion standing in Nanaimo, B.C. on the old HBC site which you can see in this photo.