Billionaire businessman and major conservative donor David Koch has died. He was 79. New Yorker reporter Jane Mayer first tweeted news of his death on Friday morning. Details of his death are not yet known, but it’s been reported that the younger Koch brother had been in poor health.

Last year Koch had stepped away from his role at Koch Industries, the multinational corporation run by his older brother Charles in Kansas. He also left the board of the Americans for Prosperity Foundation, a conservative political advocacy group funded by the Koch brothers.

According to Forbes, David Koch was the 11th richest man in the world with a net worth of some $42 billion. But despite holding leadership roles at the massive global conglomerate Koch Industries, David was best known for his political activism supporting conservative and libertarian policies since the 1980s. He’s used his billions throughout the years to support policies, foundations, and think tanks that promote small government and free market ideals.

Koch himself launched an unsuccessful bid in 1980 for Vice President on the Libertarian Party ticket as running mate with Ed Clark. They received roughly 1% of the vote. Koch has been targeted by Democratic politicians like President Obama for his involvement in politics, accusing Koch of buying elections and having too much influence on American policy and legislation.

Ahead of 2018’s midterm elections Koch aides pledged to spend an eye-popping $400 million to help secure victory for Republicans, including a $20 million pledge to shore up support for the Tax Cuts and Jobs Act.

David Koch was also known for his philanthropy, with the brothers donating over $1 billion throughout the years to causes including medical research, higher education, and public television, among other initiatives. In 2014, Koch pledged to donate $1 million to the September 11 Memorial and Museum.

The Koch legacy

Though Koch is best known for his foray into American politics, it is his involvement in business through Koch Industries that David has touched most American lives.

“In fact, this really is one of the most important companies in the United States,” “Kochland” author Charles Leonard said recently on Yahoo Finance. “Koch Industries’ annual sales are larger than that of Facebook, Goldman Sachs, and U.S. Steel combined. And it’s not just the size of the company, I think, that makes it important; it’s the scope of what it does.”

With a valuation of roughly $140 billion, the sprawling conglomerate controls subsidiaries in the manufacturing, refining, and distribution of various energy resources, such as petroleum and chemicals. Its prodigious reach has ensured that, for nearly four decades, Koch Industries has entered the lives of countless Americans.