FedEx Corporation, formerly Federal Express Corporation and later FDX Corporation, is an American multinational conglomerate holding company which focuses on transportation, e-commerce and business services which is headquartered in Memphis, Tennessee. The name "FedEx" is a syllabic abbreviation of the name of the company's original air division, Federal Express, which was used from 1973 until 2000. FedEx today is best known for its air delivery service, FedEx Express, which was one of the first major shipping companies to offer overnight delivery as a flagship service. Since then, FedEx also started FedEx Ground, FedEx Office (originally known as Kinko's), FedEx Supply Chain, FedEx Freight, and various other services across multiple subsidiaries, often meant to respond to its main competitor, UPS. FedEx is also one of the top contractors of the US government and assists in the transport of some United States Postal Service packages through its service FedEx SmartPost.