XTO Energy Inc. is an energy company, principally operating in the United States, specializing in the drilling and production of unconventional oil and natural gas assets, typically from shale rock through a process known as hydraulic fracturing. It is a subsidiary of Exxon Mobil Corporation. The acquisition of XTO Energy in 2010 made ExxonMobil the largest producer of natural gas in the U.S. Since then, XTO Energys resource portfolio has tripled through several acquisitions. The company owns interests in approximately 40,000 active oil and natural gas sites across North America. XTO Energy is an energy producer based in Fort Worth, Texas which has operated as a subsidiary of ExxonMobil since 2010. It is involved with the production, processing, transportation, and development of oil and natural gas resources. The company specializes in developing shale gas via unconventional means like hydraulic fracturing and horizontal drilling.