Crown Castle International Corp. is an American corporation headquartered in Houston, Texas, which provides infrastructure for broadcasting and mobile telephony. It operates in the United States, Puerto Rico and Australia. It provides mobile telephone coverage to 92% of the Australian population and 68 of the top 100 markets in the US on behalf of service providers such as 3, AT&T Wireless, Cingular, Telefónica O2, Nextel, Orange, Sprint PCS, T-Mobile, Verizon, and Vodafone. - Source: Wikipedia