MCI was instrumental in legal and regulatory changes that led to the breakup of the Bell System and introduced competition in the U.S. telephone industry.

The initial business plan was for the company to build a series of microwave radio relay stations between Chicago, Illinois, and St. Louis, Missouri.

The relay stations would then be used to interface with limited-range two-way radios used by truckers along U.S. Route 66 or by barges on the Illinois Waterway.

The long-distance communication service would then be marketed to shipping companies that were too small to build their own private relay systems.

[2] Hearings on the company's initial license application between February 13, 1967, and April 19, 1967, resulted in a recommendation of approval by the FCC.

In 1968, William G. McGowan, an investor from New York with experience in raising venture capital, made an investment into the company large enough to pay all outstanding debts and create a cash reserve.

[7] While MCI was performing this lobbying, the President's Task Force on Communication Policy issued a report recommending that specialized common carriers be allowed free access into the private line business.

[8] On 14 August 1969, the FCC issued a final ruling on Docket 16509, MCI's licensing request to begin building microwave relay stations between Chicago and St. Louis.

[8] The company then began to form subsidiary corporations and file applications with the FCC to create microwave relays between other city pairs.

Between September 1969 and February 1971, 15 new regional carriers were created, allowing for interconnection between several major cities in the United States.

[9] In July 1969, MICOM purchased a participating interest in Interdata, an independent regional carrier that was applying to build a microwave relay chain between New York City and Washington, D.C.[10] MCI began selling data transmission services to paying customers on January 1, 1972.

[11] To pay for the microwave transmission and relay equipment needed for build-out, MICOM began a series of private stock offerings in May 1971.

[12] In July 1971, MICOM was restructured into MCI Communications, and the company began the process of absorbing the regional carriers into a single corporation.

In the MCI version, when the husband asked the wife why she was crying, she replied "I just received my phone bill"... after which an announcer's voice stated "You're not talking too much, you're just paying too much.

[21] In 1983, Michael Milken and Drexel Burnham Lambert raised a $1.1 billion hybrid security, at the time the largest debt financing in history, for the company.

Actors Phil Hartman, Chris Rock, and Arsenio Hall starred in some of its commercials,[27] but the most commonly used spokesperson was the fictional Eva Save-a-lot, played by actress Alyssa Milano.