The Bell System was a system of companies. The companies were led by the Bell Telephone Company and later by AT&T (the American Telephone and Telegraph Company). The Bell System provided telephone service to most of the United States and Canada. Some times, it was a monopoly.
The Bell System companies were founded in 1877. People called the Bell System "Ma Bell".
On December 31, 1983, the system was divided into independent companies, known as Baby Bells and RBOCs (Regional Bell Operating Companies).
In 1994-95, Southwestern Bell changed its corporate name to SBC Communications. Between 1997 and 1999, SBC bought Pacific Telesis, SNET and Ameritech.
In 2000, Bell Atlantic bought GTE (General Telephone and Electronics Corporation. The corporate name was changed to Verizon. Also in 2000, Qwest bought US West. The surviving company was Qwest Communications.