 The borough encompasses Petersburg and Kupreanof, plus mostly uninhabited areas stretching to the Canadian–American border and the southern boundary of the City and Borough of Juneau.While the city of Petersburg ceased to exist as a separate administrative entity (the borough assembly created a service area to assume operation of the former city's services), the tiny city of Kupreanof remains separate within the borough.Tlingits from Kupreanof Island had long used a summer fish camp at the north end of Mitkof Island.