Crown Castle International Corp. is an American corporation headquartered in Houston, Texas, which provides infrastructure for broadcasting, mobile telephony and wireless broadband including small cell, traditional cell sites, rooftop sites and indoor/outdoor distributed antenna systems. It operates in the United States, including Puerto Rico. It provides mobile telephone coverage to all of the top 100 markets in the US on behalf of service providers such as Verizon, AT&T Mobility, Sprint and T-Mobile. In 2015, the company ranked #166 in the S&P 500 index.

On August 31, 2004 Crown Castle completed the sale of its UK subsidiary, Crown Castle UK, to National Grid Transco plc for $2.035 billion in cash National Grid Transco plc was renamed as National Grid plc in July 2005, while Crown Castle UK was renamed National Grid Wireless in October 2005.

On January 12, 2007, Crown Castle completed the acquisition of Global Signal Inc., a rival U.S. tower operator which was based in Sarasota, Florida.

On December 11, 2011, Crown Castle announced a definitive agreement to purchase NextG Networks, Inc. for about $1.0 billion. NextG had over 7,000 distributed antenna system nodes on-air at the time of the agreement with another 1,500 nodes under construction as well as rights to more than 4,600 miles of fiber optic cables.

On September 28, 2012, Crown Castle entered a tower leasing agreement with T-Mobile USA. The deal leases 7,200 wireless towers to the company for a term of 28 years in exchange for $2.4 billion. After the deal ends in 2040, Crown Castle may be able to purchase the towers for an additional $2.4 billion.

On October 20, 2013, Crown Castle entered a tower leasing agreement with AT&T Mobility. The deal leases 9,700 wireless towers to the company for a term of 28 years in exchange for $4.85 billion. Crown Castle also gained the right to acquire the towers outright in the future for $4.2 billion. 600 towers will be acquired outright by Crown Castle in the future. AT&T will pay $1,900 a month per site to access the towers with rent rising approximately 2% per year.

In 2015, Crown Castle expanded into small cell technology to boost the capability and widen the scope of their network. The acquisition of Quanta Fiber Networks (Sunesys) in 2015 ensured that the company had access to over 10,000 miles of fiber in key metro areas like Los Angeles, Chicago, Silicon Valley and Atlanta, this followed the 2014 acquisition of 24/7 Mid-Atlantic Network with over 800 miles of fiber along the East Coast of the United States.

On July 19, 2017, Crown Castle signed a definitive agreement to acquire Lightower for approximately $7.1 billion in cash. Lightower is a fiber network operator primarily in the northeast United States. This transaction increases Crown castle's fiber network to approximately 60,000 route miles. The buyout had a significant impact on second-quarter earnings reported in late July. Revenue increased by 3.3% and small cells increased sales by 42%. Crown Castle also announced a $3.25 billion common stock offering as well as a $1.5 billion sale of convertible preferred shares to help finance the Lightower purchase.