  st. petersburg is a borough in clarion county, pennsylvania, united states. the population was 400 at the 2010 census. ==geography== st. petersburg is located at . according to the united states census bureau, the borough has a total area of , all of it land. ==demographics== {{uscensuspop |1880=1044 |1890=655 |1900=482 |1910=453 |1920=454 |1930=487 |1940=510 |1950=451 |1960=417 |1970=416 |1980=452 |1990=349 |2000=405 |2010=400 |estimate=394 |estyear=2012 |footnote=sources:{{cite web|url=h
Boroughs_in_Clarion_County,_Pennsylvania