What is Center City Philadelphia?

This question may sound strange, especially to a native Philadelphian but it is actually not a strange question. This is why I feel that we should add definition to our project. Center City, or downtown Philadelphia is located between the Delaware River and the Schuylkill River

The Delaware River

Schuylkill River

and for our mapping purposes, between South Street and Spring Garden Street. Some may include more streets and some may exclude a couple but our Center City Green Map will be defined by these boundaries.
Google Map of Center City Philadelphia