1879 Bell merges with the New England Telephone Company to form the National Bell Telephone Company .
10 September1879 Connolly and McTighe patent a "dial" telephone exchange (limited in the number of lines to the number of positions on the dial.).
1880 National Bell merges with others to form the American Bell Telephone Company .
1882 A telephone company --an American Bell affiliate-- is set up in Mexico City.
1885 American Telephone and Telegraph Company AT&T is formed.
1886 Gilliland's Automatic circuit changer is put into service between Worcester and Leicester allowing for the first Operator dialing allowing one operator to run two exchanges.
1899 AT&T becomes the overall holding company for all the Bell companies.
November 21889 A. G. Smith patents a telegraph switch which provides for trunks between groups of selectors allowing for the first time, fewer trunks than there are lines, and automatic selection of an idle trunk.
1915 Vacuum tubes used in coast-to-coast telephone circuits
1919 AT&T installs the first dial telephones in the Bell System, in Norfolk VA. The last manual telephones in the system were not converted to dial until 1978.