American Tower (NYSE: AMT) leases over 27,000 cell phone towers to wireless service providers, including Verizon Communications (VZ), Sprint Nextel (S) and AT&T (T). It operates over 20,000 wireless towers in the U.S. and has an additional 7,000 in Mexico, Brazil, and India.^[1] With a US market share over 40%, the company is one of the largest wireless tower operators in the country, just behind leader Crown Castle International (CCI).

Cell phone towers derive revenue from multiple tenants who use the infrastructure simultaneously. Because of the regulatory difficulty of building new towers (at least domestically), growth is largely driven by adding tenants to existing towers. This gives the tower companies significant barriers to entry and strong cash flow from incremental business at each tower.

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