CenturyLink, Inc. is an American worldwide communications company headquartered in Monroe, Louisiana. It provides communications and data services to residential, business, governmental and wholesale customers in 36 states. A member of the S&P 500 index, the company operates as a local exchange carrier and Internet service provider in U.S. markets and is the third-largest telecommunications company in the United States in terms of lines served, behind AT&T and Verizon. It also provides long distance service.