Beginning in the 1910s, American antitrust regulators had been observing and accusing the Bell System of abusing its monopoly power, and had brought legal action multiple times over the decades.

Under the commitment, AT&T escaped break-up or nationalization in exchange for divesting itself of Western Union and allowing non-competing independent telephone companies to interconnect with its long-distance network.

Proliferation of telephone service allowed the company to become the largest corporation in the world until its dismantling by the United States Department of Justice in 1984, at which time the Bell System ceased to exist.

[2][4] In response to the threat of antitrust action from government, AT&T entered into an out-of-court agreement, known as the Kingsbury Commitment with the Department of Justice in 1913.

[2][5] AT&T committed to sell its $30 million in Western Union capital stock, allow competitors to interconnect with its long-distance telephone network, and not acquire other independent companies without permission from the Interstate Commerce Commission.

Member telephone companies paid a fixed fraction of their revenues as a license fee to Bell Labs.

In 1949, the United States Department of Justice alleged in an antitrust lawsuit that AT&T and the Bell System operating companies were using their near-monopoly in telecommunications to attempt to establish unfair advantage in related technologies.

The outcome was a 1956 consent decree limiting AT&T to 85% of the United States' national telephone network and certain government contracts, and from continuing to hold interests in Canada and the Caribbean.

[8] The Bell System also owned various Caribbean regional operating companies, as well as 54% of Japan's NEC and a post-World War II reconstruction relationship with state-owned Nippon Telegraph and Telephone (NTT) before the 1956 boundaries were emplaced.

Even during the period from 1956 to 1984, the Bell System's dominant reach into all forms of communications was pervasive within the United States and influential in telecommunication standardization throughout the industrialized world.

It resulted from another antitrust lawsuit filed by the U.S. Department of Justice in 1974, alleging illegal practices by the Bell System companies to stifle competition in the telecommunications industry.

Northern Electric and the Caribbean regional operating companies were considered part of the Bell System proper before the break-up.

The operation of Japan's NTT during the post-World War II occupation was considered an administrative adjunct to the North American Bell System.

[citation needed] Of the various resulting 1984 spinoffs, only BellSouth actively used and promoted the Bell name and logo during its entire history, from the 1984 break-up to its reunion with the new AT&T in 2006.

Similarly, cessation of using either the Bell name or logo occurred for many of the other companies more than a decade after the 1984 break-up as part of an acquisition-related rebranding.