The history of MCI is an exciting story of the origins and development of the modern telecommunications world. Before MCI there was one dominant company in the industry, AT&T, and most Americans leased rotary telephones and subscribed to POTS, plain old telephone service. MCI initiated the breakup of the Bell System, inaugurated competition in telecommunications, introduced a plethora of technological advances and new service offerings, and changed the way people throughout the world thought about and used telecommunications.