Billionaire industrialist David H Koch, who with his older brother Charles was both celebrated and demonised for transforming American politics by pouring their riches into conservative causes, died Friday at 79.
The cause of death was not disclosed, but Koch Industries said Koch, who lived in New York City, had contended for years with various illnesses, including prostate cancer.
A chemical engineer by training, Koch was an executive in the family-run conglomerate, the Libertarian Party's vice-presidential candidate in 1980 and a major benefactor of educational, medical and cultural organisations.
But he and his brother became best known for building a political network dubbed the "Kochtopus" for its far-reaching support of conservative and libertarian causes and candidates.
The brothers in 2004 founded the anti-tax, small-government group Americans for Prosperity, which continues to be one of the most powerful conservative organizations in US politics.
"I was taught from a young age that involvement in the public discourse is a civic duty," David Koch wrote in a 2012 op-ed in the New York Post.
"Each of us has a right indeed, a responsibility, at times to make his or her views known to the larger community in order to better form it as a whole. While we may not always get what we want, the exchange of ideas betters the nation in the process."
"I have a point of view. When I pass on, I want people to say he did a lot of good things, he made a real difference, he saved a lot of lives in cancer research."