For statistical purposes, the First Nations reserves of Eskasoni 3 and Membertou 28B are included in the county, but are separate entities.

By proclamation of October 17, 1763 after termination of the Seven Years' War, Cape Breton Island was formally annexed to Nova Scotia.

From 1784 to 1820, Cape Breton Island was established as a separate colony with a Lieutenant Governor and a nominated Executive Council, but without an elected house of assembly.

Not until after Cape Breton Island was re-annexed to Nova Scotia in 1820 did it receive representation in an elected legislature.

The new regional municipality's boundary included all of Cape Breton County except for the Eskasoni and Membertou First Nations.