1974    The United States Department of Justice files its final anti-trust suit against AT&T. This suit later leads to the break up of AT&T and its Bell System.

1982    The break up of AT&T: AT&T agrees to divest itself of twenty-two subdivisions.

1983    Ameritech Mobile Communications (now AT&T) launched the first US cellular network in Chicago, Illinois.

1983    The AT&T Bell System is broken up by the United States Government.

1990    AT&T's long distance telephone network suffers a cascade switching failure.