Petersburg is a city in Petersburg Census Area, Alaska, in the United States. According to 2009 Census Bureau estimates, the population of the city is 2,824 full time residents.
Petersburg is located on the north end of Mitkof Island, where the Wrangell Narrows meets Frederick Sound. Petersburg is halfway between Juneau, 190 km (120 mi) to the north, and Ketchikan, 180 km (110 mi) to the south.
According to the United States Census Bureau, the city has a total area of 46.0 square miles (119 km sq), of which, 43.9 square miles (114 km sq) of it is land and 2.2 square miles (5.7 km sq) of it (4.74%) is water. Small cruise-ships (up to 250 passengers) and private yachts visit from May through September.