You can find ZIP Codes and post office locations, and track a package with online tools from the U.S. Postal Service (USPS).   ZIP Code Use the ZIP Code lookup tool to search for a ZIP Code by address, city, company name, or partial address. You can also search for all city/town names in a ZIP Code. Post Office Use the Post Office Locator to search for post offices, approved postal providers, self service kiosks, collection boxes, and other services.