Post Offices List in Irwin City, Pennsylvania:
| Irwin Post Office | 140 Main St, Irwin, PA 15642 |
| North Huntingdon Post Office | 1101 Main St, Irwin, PA 15642 |
| Irwin Post Office | 140 Main St, Irwin, PA 15642 |
| North Huntingdon Post Office | 1101 Main St, Irwin, PA 15642 |