Pennsylvania Third Class Cities are municipalities with a population of at least 10,000 but less than 80,000 residents.

Third Class Cities:

> Third class cities operate under a commission form of government, with a Mayor and four Councilmen. The Mayor is a   member and serves as president of the council. All third class cities are governed by the Third Class City Code.
> There are 37 third class cities in Pennsylvania.
> Each Councilman and Mayor is in charge of one of the city’s major departments.
> These officials and the controller and treasurer are elected at-large for four-year terms.
> Appointments of all other city officers and employees are made by the council.

The City of Sunbury is a "Third Class City"