 Petersburg incorporated as a borough in January 2013, encompassing Petersburg and Kupreanof, plus mostly uninhabited areas stretching to the Canada–US border and the southern boundary of the City and Borough of Juneau.While the City of Petersburg ceased to exist as a separate 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.Petersburg is located on the north end of Mitkof Island, where the Wrangell Narrows meets Frederick Sound.