T imothy Dunn is an American billionaire whose wealth is derived from his family's stake in the telecommunications infrastructure giant, Crown Castle International. The company is the largest provider of shared communications infrastructure in the United States, with a massive portfolio of over 40,000 cell towers, as well as a vast network of fiber optic cable. The company's business model is to lease space on its towers and fiber network to major wireless carriers like AT&T, Verizon, and T-Mobile.

While he is not the founder of the company, his family was a key early investor and has a massive and long-held stake in the publicly traded company, which is the source of their multi-billion dollar fortune. He has served on the company's board of directors for many years, helping to guide its strategy. The family's wealth has been built on the explosive growth of the mobile communications industry, which has created a huge and growing demand for the infrastructure that Crown Castle provides.