Post Office - New Castle 435 S Cascade St New Castle, PA 16108 Phone : (724) 656-7221 Business Category Post Offices Toll-Free           (800) ASK-USPS Fax           (724) 656-7205 Passport Application Services - New Castle 435 S Cascade St New Castle, PA 16108 Phone : (724) 656-7221 Business Category Passport Application Services Toll-Free           (800) ASK-USPS Fax           (724) 656-7205