Boothia Peninsula is the northernmost area of the North American mainland and has a surface area of roughly 19,600 km2. Much of the peninsula consists of Paleozoic lowland with flat limestone sediments, low elevation, and featureless coastlines. An upland arc composed of Precambrian Shield runs through the centre of the peninsula. Granite bedrock forms rugged, rocky hills and, in the north, fault lines stretch both north-south and east-west, carving the granite into giant blocks. Boothia peninsula is at its most rugged in the south, where west-facing escarpments extend from Sagvak Inlet to Lord Lindsay Lake.
The Boothia Isthmus is a thin, lake-filled strip of land that connects Boothia Peninsula to the mainland. North of Middle Lake lies a till plain, where moraines dot the landscape and flat-bedded sediments form 150-m high rounded hills, with crystalline rocks encircling their bases.
Taloyoak, on Spence Bay, and Mission, on Thom Bay, are the only two settlements on the Boothia Peninsula and have a combined population of more than 800 people.