Petersburg is a city in Washington Township, Pike County, in the U.S. state of Indiana. The population was 2,383 at the 2010 census. The city is the county seat of Pike County.
Petersburg is part of the Jasper Micropolitan Statistical Area.
Petersburg was laid out in 1817. The city was named for Peter Brenton, an original owner of the town site. A post office has been in operation at Petersburg since 1823.
Petersburg is located at 38°29′30″N 87°16′49″W (38.491653, -87.280372).
According to the 2010 census, Petersburg has a total area of 1.474 square miles (3.82 km2), of which 1.47 square miles (3.81 km2) (or 99.73%) is land and 0.004 square miles (0.01 km2) (or 0.27%) is water. The lower portion of the White River runs through the city.
The climate in this area is characterized by hot, humid summers and generally mild to cool winters. According to the Köppen Climate Classification system, Petersburg has a humid subtropical climate, abbreviated "Cfa" on climate maps.
As the 2010 census, there were 2,383 people, 1,025 households and 592 families living in the city. The population density was 1,621.1 inhabitants per square mile (625.9/km2).