Crown Castle owns and leases roughly 40,000 cell towers in the United States. It leases space on its towers to wireless service providers, which install equipment to support their wireless networks. The company has a very concentrated customer base, with about 75% of its revenue from the Big Three US mobile carriers: Verizon, T-Mobile, and AT&T. Crown has announced plans to divest its fiber business, which is expected to be finalized in 2026. After that, it will be a stand-alone tower operator. Crown Castle operates as a real estate investment trust.