David Koch, the industrialist and libertarian who used his fortune to transform American politics while also donating more than $1bn to philanthropic causes, has died at the age of 79.

Koch, whose net worth of about $59bn according to the Bloomberg Billionaires Index, tied him with his brother as the world's seventh-richest person, derived most of his wealth from a 42% stake in Koch Industries, which has annual revenue of about $110bn.

A resident of New York's Upper East Side and the city's richest person, Koch once joked that Koch Industries was "the biggest company you've never heard of". The conglomerate has interests ranging from oil and ranching to farming and the manufacturing of electrical components.

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But he and Charles Koch (83) became better known for pushing their views than their business acumen, pumping millions into conservative causes and candidates.

The operation they built includes more than 700 donors who give $100 000 or more a year and a group called Americans for Prosperity that has chapters in 35 states. It's rivaled only by the Republican Party in its influence on the conservative agenda in the US.

The Koch brothers and other wealthy donors were able to expand their influence on elections following the Supreme Court's 2010 Citizens United decision that paved the way for unbridled spending, both directly and indirectly, by outside groups.

Koch money incubated a generation of political figures, including Vice President Mike Pence, Secretary of State Mike Pompeo, former Environmental Protection Agency Administrator Scott Pruitt, Energy Secretary Rick Perry and Wisconsin Governor Scott Walker.

Yet all those men but Walker worked for President Donald Trump, who has upended the free-market views the Kochs have tried to foster within the Republican Party. That has prompted clashes with Trump, especially on trade and immigration policy.

The brothers didn't support Trump in his 2016 campaign, although they praised his efforts to cut taxes and regulations.

Koch was the vice presidential candidate for the Libertarian Party in 1980. But as his health failed, he became less prominent in the Koch political operation.

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In June 2018, Charles Koch told company employees that his brother would step down from the business and political empires because of health problems. Charles Koch's letter didn't provide details.

New York philanthropist Adrienne Arsht said David Koch never acted like Manhattan's wealthiest person.

"He was most understated," she said. "There was nothing about anything that he did that made you think he was anything but a man from Kansas."

But the Koch brothers played a massive role in politics, helping shape state and federal policy.

"By lavishly underwriting candidates, policy organizations, and advocacy groups - often through untraceable donations - they have pulled American politics toward their own arch-conservative, pro-business, anti-tax, and anti-regulatory agenda," Jane Mayer, who has covered the Koch brothers for the New Yorker, wrote in June 2018.

The brothers were credited with helping underwrite the limited-government Tea Party movement that helped Republicans take control of Congress in 2010.

The brothers favored ending the minimum wage, eliminating so-called "corporate welfare" for new factories and stadiums and backed union-weakening laws.