Crown Castle owns or manages roughly 40,000 wireless 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 90% of its revenue from the Big Three US mobile carriers: Verizon, T-Mobile, and AT&T. Crown Castle has plans to divest its fiber business, which is expected to be finalized in the first half of 2026. After that, it will be a stand-alone tower operator. Crown Castle operates as a real estate investment trust.