§ 107. Classes of cities. (a) City of the first class. A city with a
population of one hundred seventy-five thousand or more.

(b) City of the second class. A city with a population of fifty
thousand and less than one hundred seventy-five thousand.

(c) City of the third class. Any city not included in the foregoing
classes.

(d) The classification herein made shall be determined by the federal
census or state enumeration, whichever is the later, as last previously
taken before the effective date of this chapter.