Billionaire industrialist David Koch, who with his older brother Charles was both celebrated and demonized 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 organizations.
But he and his brother became best known for building a political network in 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 U.S. politics.
While lionized on the right, the Koch brothers have been vilified by Democrats, whom they often targeted.
The Kochs invested heavily in fighting President Barack Obama's health care overhaul; they fought to bring conservative voices to college campuses; and they developed a nationwide grassroots network pushing conservative causes and candidates at the state and national levels.