The alphamegalog of the cities of Pennsylvania lists the largest city in Pennsylvania for each letter of the alphabet. In this case, ‘largest’ is based on population within the city proper.

Allentown
Bethlehem
Chester
Drexel Hill
Erie
Fullerton
Greensburg
Harrisburg
Indiana
Johnstown
King of Prussia
Lancaster
Monroeville
Norristown
Oil City
Philadelphia
Quakertown
Reading
Scranton
Taylor
Upper Darby
Valley Forge
Wilkes Barre
(no X)
York
Zelienople