Crown Castle International Corporation is a leading independent owner and operator of shared wireless infrastructures, including extensive networks of towers. Its core business involves the engineering, deployment, marketing, ownership, operation and leasing of shared-wireless communications sites. The company has led the industry in such activities as the first outsourcing of a United States tower infrastructure network. It has experience with large-scale tower portfolio management and strategic relationships. Its tenants include Verizon Wireless, Cingular, T-Mobile, Nextel, Sprint PCS and AT&T Wireless Services, as well as various state and federal government agencies and broadband data service providers. Crown Castle s United States operations currently employ more than 600 staff in 32 field offices throughout the country, including six regional offices and a number of district office locations. Crown Castle International Corporation maintains head offices in Houston.