Simmons died Saturday night at Baylor University Medical Center at Dallas. Annette Simmons said her husband was "very sick for the last two weeks," the Dallas Morning News reported.
After jobs with the U.S. Civil Service Commission, the Federal Deposit Insurance Corp. and Republic National Bank of Dallas, Simmons bought a pharmacy and built it into a 100-store chain he sold in 1973 for $50 million in stock.
He spent the rest of his career buying and selling companies under his privately held Contran Corp., the Morning News said. His business holdings included steel, chemicals, sugar beet processing and vineyards.
"I never bought anything with the idea of selling it," he said in a 2007 interview with the newspaper. "I have eventually sold things, but only when the environment had changed and it wasn't the right time to hold it.
The newspaper said Simmons, who was ranked 40th on Forbes' list of the 400 wealthiest Americans, was a philanthropist whose donations totaled in the hundreds of millions of dollars.
"Harold accomplished so much in his life," fellow Dallas billionaire T. Boone Pickens said Sunday in a written statement. "He was a passionate person -- passionate about his family, his business, philanthropy and politics. We worked together on a lot of different projects. He was one of the most successful and focused men I've ever known. We should all leave such a rich legacy behind."
Simmons married his wife Annette in 1980. Other survivors are four daughters from two previous marriages and two stepchildren.
Simmons' personal life had its downside. He essentially banished two of his four daughters who sued over his handling of their family trusts, paying $50 million each to Scheryle Patigian and Andrea Swanson to end their lawsuits.
Simmons also drew criticism from environmentalists for a hazardous-waste dump near Andrews, owned by his Waste Control Specialist Co., which began accepting low-level radioactive waste last year.
A political conservative, he was one of the nation's top campaign financiers, doling out nearly $31 million in the 2011-12 election cycle, the Morning News said.
Simmons told the Wall Street Journal during the 2012 election campaign he believed President Obama was a socialist who was "the most dangerous American alive ... because he would eliminate free enterprise in this country."
Bush issued a statement extending his condolences to the Simmons family.
"Dallas has lost a generous benefactor to many worthy causes. And we, like many others, have lost a friend in Harold," the former Republican president said.