In Short

AT&T (NYSE: T) — originally American Telephone & Telegraph — is headquartered in Dallas, Texas. The largest iPhone, iPad in the United States, AT&T is the nation's second-largest wireless carrier, behind Verizon.

AT&T's lineage runs directly back to the original Bell Telephone Company founded by Alexander Graham Bell. American Telephone & Telegraph — AT&T — was originally established in 1885.

While AT&T faced some competition in the early days, its ascendancy was all but certain by the early part of the 20th century. AT&T entered an arrangement with the United States government that virtually assured it would have a monopoly on telephone service for the U.S. market throughout most of the 20th century,

In 1984 U.S. regulators dissolved AT&T's monopoly, turning "Ma Bell" into regional operations (known as "Baby Bells") and allowing for more competition in the long distance market. Southwestern Bell was one of these. The company eventually purchased that AT&T name and brand; today's AT&T is an outgrowth of that.

AT&T has a prominent place in the history of Apple: It was AT&T that agreed to carry the iPhone (under its previous moniker Cingular) in 2007. The phenomenally popular phone drove many customers to AT&T, which had an exclusive for the lucrative United States market until 2011, when AT&T's biggest rival, Verizon, began to carry the phone.

AT&T is no longer the exclusive iPhone carrier, nor were they the first to launch an LTE network in the U.S., but they remain one of the most popular iPhone carriers and one of the fastest networks.