Why was birch bark useful for making canoes?

Birch bark was highly valued by North American Indians for canoe construction primarily because it is thin and water-impervious.1

These properties made it an ideal material for creating a lightweight, durable outer shell for watercraft. To build a canoe, pieces of the bark were sewn together using roots and then caulked with resin to ensure the vessel remained watertight. The bark was then stretched over a rigid frame of ribs and sheathing, which were pressed into place and supported by a gunwale. This design was so efficient and well-suited for wilderness travel that it was widely adopted by European explorers and later used extensively during the fur trade.123