Banks Island, the most westerly of the Arctic islands, has three main topographical regions: a plateau in the north, a plateau in the south, and central lowlands. The northern plateau forms cliffs on its ocean margins and drops sharply down to the central lowlands on its inland border. Towards the east, the plateau has undergone erosion, so hills descend gradually to form undulating lowlands. The rest of the lowlands have small hills, and wide river valleys, but are otherwise so flat that they have been compared to the Prairies. Their surface is covered with debris left behind by retreating glaciers.
The southern plateau is composed of sedimentary and volcanic bedrock. The Masik River, which runs from the east coast to an outlet on the western edge of the island, separates the plateau from the central lowlands. The Big, Bernard, and Thomsen rivers also traverse the island, all flowing from east to west. These rivers run through wide valleys that are hard to see once snow has fallen.
Robert McClure was the first European to visit Banks Island. After mapping its coastal regions, his ship, Investigator, became trapped in ice. Contrary to his expectations, the ice did not break up over the next summer; however, his crew was rescued from starvation by the arrival of another ship. At this time, no Inuit were living on the island, though hunting parties visited regularly from nearby Victoria Island. In the 1950s, a settlement was established at Sachs Harbour, on the southwest corner of the island, and had reached a population of 135 by 1966.