MCI Communications Corporation (MCI) was a large telecommunications company. It was organized in October 1963 in Joliet, Illinois, by John D. "Jack" Goeken (1930-2010) as Microwave Communications, Inc. Goeken and his partners were planning to provide point-to-point private line microwave communications between Chicago and St. Louis to small businesses that could not afford the high telephone rates offered by American Telephone and Telegraph Company (AT&T)--a de facto monopoly of United States telecommunications at that time. The Federal Communications Commission (FCC) approved an application from Microwave Communications to construct and operate a private microwave system in August 1969. The approval opened an era of competition in the telecommunications industry.

William G. McGowan (1927-1992), who joined the company in 1968, brought in a different vision of its future--participation in constructing a nationwide common carrier communications system. In August 1968, McGowan incorporated a new company, Microwave Communications of America (MICOM), which changed its name to MCI Communications Corporation, Inc. (MCI) in July 1971. MICOM was created to sponsor the development of affiliated regional companies with local financing, and Microwave Communications became one of sixteen such companies. By March 1971, all regional companies had filed for construction permits for their section of the planned nationwide network. In August 1972, MCI acquired Interdata Communications, Inc., which controlled a New York-Washington microwave route. In February 1973, MCI Telecommunications Corporation (MCIT) was formed as a long-distance communications subsidiary of MCI, and during the 1970s, all regional carriers merged into it.

AT&T and its affiliated local Bell Companies used their control over local networks as leverage for rate increases and denied connections to their network by MCI and other common carriers. In 1973, with McGowan's (CEO) and MCI senior vice president of regulatory affairs Kenneth A. Cox's (1916-) testimonies at the Senate subcommittee, MCI launched a campaign against AT&T for violating U.S. antitrust laws. A decade-long regulatory and legal battle changed the essence of telecommunications in the United States. By the final judgment of the antitrust suit of the U.S. Department of Justice against AT&T (1974-1982), AT&T was divested from its regional companies, and all telecommunications companies received equal access to their network facilities starting from January 1, 1984.

After winning the right to connect its network to local systems, MCI faced another challenge--it had to fight for the business of government, commercial, and residential markets. Before 1984, these customers had no choice of telecommunications carrier and used to think of AT&T as the only reliable service provider.

MCI was the first American company seriously engaged in implementing fiber optic technology. In 1983, it ordered more than 150,000 miles of single-mode fiber optic cable; in March 1984, the Washington, D.C–New York segment of the new system became operational; in 1989, MCI owned two complete transcontinental fiber optic networks that carried a large volume of voice and data traffic at high speeds with high quality. MCI was also the second largest U.S. owner in a joint venture of the first transatlantic fiber-optic telephone cable. When, in December 1991, MCI converted its entire network from analog to digital transmission, its modernized system turned into an "intelligent network," which was compatible with other international networks and allowed the company to market new services and attract new business partners in the last decade of the twentieth century.

Positioning itself as a company ready to get into the information age ahead of its competitors and to offer customers integrated global voice, data, and networking services, MCI in 1993 developed the "networkMCI" strategy that consisted of several components: creation of a nationwide information superhighway, entry into local telecommunications, building a wireless network integrated with MCI's products, and formation of global alliances in order to provide seamless services to multinational customers.

In the late 1990s, MCI sought a partner in order to increase capital for more efficient competition with domestic and international carriers. After canceling a proposed merger with British Telecommunications Corporation (BT), MCI entered into a merger with the rapidly growing telecommunications firm WorldCom. The agreement, completed on September 15, 1998, created MCI WorldCom, Inc., which provided local, long-distance, and international full-range telecommunications services such as voice, data, internet, and wireless. To separate its two distinct businesses, at the end of 2000, WorldCom, Inc. arranged two business groups under its umbrella: WorldCom group (high-growth data, internet, hosting, and international businesses) and MCI group (high-cash flow consumer, small business, wholesale long-distance voice and dial-up internet access). It also created two separately traded stocks. The corporation received an SEC Inquiry in April 2002 regarding its capital expenditure accounting irregularities and, as a result of independent audits and financial investigation, filed for bankruptcy on July 21, 2002. Under the Plan of Reorganization filed by WorldCom, Inc. with the U.S. Bankruptcy Court in April 2003, the company changed its brand name to MCI. In 2006, the company was bought by Verizon.