RBOCs (Regional Bell Operating Companies):

When AT&T was split in the mid-1980s, seven RBOCs, or "Baby Bells" resulted.
They are:

Pacific Bell (Pacbell) (Operates in California)
Southwestern Bell (Operates in Missouri, Oklahoma, Kansas, Arkansas, and
  Texas)
U.S. West (Operates in Washington, Oregon, Idaho, Montana, Utah, Colorado,
  New Mexico, Arizona, Nebraska, Wyoming, Iowa, North Dakota, South Dakota,
  and Minnesota)
BellSouth (Operates in Florida, Georgia, North Carolina, South Carolina,
  Alabama, Louisiana, Kentucky, Tennessee, and Mississippi)
Bell Atlantic (Operates in Pennsylvania, Maine, New Hampshire, Vermont,
  Connecticut, New Jersey, Delaware, Maryland, Virginia, West Virginia, New
  York (Except New York City), Massachusetts, and Rhode Island)
NYNEX (New York/New England Exchange) (Operates in New York City)
Ameritech (Operates in Michigan, Wisconsin, Illinois, Indiana, and Ohio)
Bellcore (Bell Communications Research) (The research and development branch)