The U.S. Postal Service is the only delivery service that reaches every address in the nation: 160 million residences, businesses and Post Office Boxes.
USPS is an independent agency of the executive branch of the United States federal government responsible for providing postal service in the United States, including its insular areas and associated states.
The USPS Web Tools API library gives eCommerce website shopping carts and shipping software access to valuable USPS data—free of charge! You can check shipping rates, track packages, and schedule a package pickup all through USPS Web Tools.