Pacific Telesis was a telecommunications company based in the United States, primarily serving the western region. It was formed in 1984 as a result of the breakup of AT&T, focusing on providing local telephone services and related communications. In 1997, Pacific Telesis merged with SBC Communications, which later became part of AT&T again after several acquisitions. The company played a significant role in the development of telecommunications infrastructure in California and Nevada, contributing to advancements in technology and service delivery in the industry.