Crown Castle International Corp., together with is subsidiaries, owns, operates, and leases shared wireless infrastructure primarily in the United States, Puerto Rico, and Australia. The company's wireless infrastructure includes towers and other structures, such as rooftops; and distributed antenna systems (DAS) networks. It is involved in the rental of space or physical capacity on its towers, DAS, and third party land interests to wireless communications companies. The company also provides network services relating to its wireless infrastructure, primarily consisting of antenna installations and subsequent augmentation services, as well as additional site development services relating to existing and new antenna installations on its wireless infrastructure, such as site acquisition, architectural and engineering, zoning and permitting, fiber installation, other construction, and other services related network development. As of December 31, 2012, it owned, leased, or managed approximately 31,500 towers. Crown Castle International Corp. was founded in 1994 and is headquartered in Houston, Texas.