United States Cellular Corporation, doing business as U.S. Cellular, is a mobile network operator which owns and operates the fourth-largest wireless telecommunications network in the United States, serving 5 million customers in 426 markets in 23 U.S. states as of the first quarter of 2017. The company has its headquarters in Chicago, Illinois.\nU.S. Cellular was formed in 1983 as a subsidiary of Telephone and Data Systems, Inc., which owns an 84 percent stake.