Entrepreneur T. Boone Pickens dead at 91

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"The long-time Dallas resident, who had battled back from a series of strokes and further head injuries sustained in a 2017 fall, died of natural causes," a statement on the tycoon's official website said.

Pickens gained wealth working in oil, KXAS reported. Born in Holdenville, Oklahoma, in 1928, Thomas Boone Pickens Jr. started working at Phillips Petroleum, spending his adult years in Texas and later founding what would become Mesa Petroleum in 1956.

"I formed my first oil and gas firm, Petroleum Exploration Inc., with $2,500 of borrowed money. It was tough work, and I, at one point, was living in my truck and shaving in gas station bathrooms," Pickens said in a letter to the class of 2018 published in Forbes. "But that firm was a predecessor company to Mesa Petroleum, the company I took public in 1964, which became one of America's largest independent natural gas and oil companies. A good plan and hard work helped me get there, but neither are possible without healthy optimism. So, be the eternal optimist."

The former billionaire was a massive supporter of his alma mater, Oklahoma State University, where he studied geology. He donated more than half of the $1 billion he gave to charity to the school, splitting it almost evenly between athletics and academics.

Other groups Pickens donated money to include Big Brothers Big Sisters of North Texas, the Center for Missing and Exploited Children, Meals on Wheels, the Center for BrainHealth at The University of Texas at Dallas, and Scottish Rite Children’s Hospital.

Pickens was considered a pioneer in the energy industry and on July 8, 2008, he launched the Pickens Plan, a self-funded grassroots campaign to reduce U.S. dependency on OPEC oil. Forbes reported he worked to increase the adoption of wind energy, solar energy and natural gas.

Plans are pending for memorial services in Dallas and Stillwater, Oklahoma, according to the official site.

Pickens is survived by his five children, Deborah Pickens Stovall, Pam Pickens Grace, Michael Pickens, Tom Pickens and Liz Pickens Cordia, 11 grandchildren and multiple great-grandchildren.