We merged with a state chartered community credit union several years ago that included the south and southwest suburbs of Chicago. Since the state approved the community can we add the community to our federal charter?

No.  State field of membership rules often differ from NCUA's rules.  Therefore, you cannot use the community portion of the field of membership of a state-chartered credit union to support an application for a federal field of membership.  As a multiple common bond credit union, your ability to serve a community is limited to adding an underserved area or converting to a community chartered credit union. Previously approved, approved in the past, application, state charter, multiple common bond, underserved, community