Crown Castle International Corp. (CCIC) owns, operates and leases towers and other communication structures, including certain rooftop installations (collectively, towers), for wireless communications. Its core business is renting space on its towers via long-term contracts in various forms, including license and lease agreements. Its towers can accommodate multiple customers for antennas and other equipment necessary for the transmission of wireless signals for mobile telephones and other devices. CCIC operates its business primarily in the United States (including Puerto Rico) and Australia, with nominal operations in Canada and the United Kingdom. It conducts its operations principally through subsidiaries of Crown Castle Operating Company, including certain subsidiaries that operate its tower portfolios in the United States, Puerto Rico and Canada (collectively referred to as CCUSA), and a 77.6%-owned subsidiary that operates its Australia tower portfolio (referred to as CCAL).