Northwestern Bell Telephone Company is an American communications provider that serves the states of the upper Midwest opposite the Southwestern Bell area, including Iowa, Minnesota, South Dakota, North Dakota, and Nebraska. As of 1991 the name Northwestern Bell is no longer the corporate identity, although Northwestern Bell is now owned by the Lumen Technologies and is therefore doing business as Lumen. Doing business as names were not begun before 2001; that is why the Northwestern Bell name was dormant but later revived by CenturyLink.

The Bell System was a system of telecommunication companies, led by the Bell Telephone Company and later by the American Telephone and Telegraph Company (AT&T), that dominated the telephone services industry in North America for over 100 years from its creation in 1877 until its antitrust breakup in 1983. The system of companies was often colloquially called Ma Bell, as it held a vertical monopoly over telecommunication products and services in most areas of the United States and Canada. At the time of the breakup of the Bell System in the early 1980s, it had assets of $150 billion and employed over one million people.