RBOC - technical definition

Also known as Regional Holding Company (RHC). In the United States, each of the seven regional companies formed by the Modified Final Judgement (MFJ), which broke up the AT&T Bell System effective January 1, 1984. Each RBOC comprised one or more of the 22 Bell Operating Companies (BOCs) that previously were wholly owned by AT&T. Over time, each RBOC fully absorbed its component BOCs, creating a single legal entity with a centralized management structure. As Cincinnati Bell and Southern New England Telephone (SNET) were not wholly owned by AT&T, they were divested as standalone operating telephone companies. Table R-1 maps the BOCs into the RBOC organizations.

Bell Operating Companies (Primary States of Operation), Pre-divestiture	Regional Bell Operating Companies (Headquarters), Post-divestiture
Illinois Bell (Illinois)	Ameritech (Illinois). Acquired by SBC Communications (October, 1999); now AT&T.
Indiana Bell (Indiana)
Michigan Bell (Michigan)
Ohio Bell (Ohio)
Wisconsin Telephone (Wisconsin)
Bell of Pennsylvania (Pennsylvania)	Bell Atlantic (Pennsylvania); now Verizon Communications.
Diamond State Telephone (Delaware)
The Chesapeake and Potomac Companies (District of Columbia, Maryland, Virginia, and West Virginia)
New Jersey Bell (New Jersey)
South Central Bell (Alabama, Kentucky, Louisiana, Mississippi, and Tennessee)	BellSouth (Georgia). Acquired by AT&T (January 2007).
Southern Bell (Florida, Georgia, North Carolina, and South Carolina)
New England Telephone (Massachusetts, Maine, New Hampshire, Rhode Island, and Vermont)	NYNEX (New York). Acquired by Bell Atlantic (August 1997); now Verizon Communications.
New York Telephone (New York)
Pacific Bell (California)	Pacific Telesis (California). Acquired by SBC (April 1997); now AT&T.
Nevada Bell (Nevada)
Southwestern Bell (Arkansas, Kansas, Missouri, Oklahoma, and Texas)	Southwestern Bell Corporation (Texas), then SBC Communications; now AT&T (November 2005).
Mountain Bell (Arizona, Colorado, Idaho, Montana, New Mexico, Utah, and Wyoming)	US West (Colorado). Acquired by Qwest (June 2000).
Northwestern Bell (Iowa, Minnesota, North Dakota, Nebraska, and South Dakota)
Pacific Northwest Bell (Oregon and Washington)