One of the wealthiest people in America, David Koch, has passed away at the age of 79. He will likely be remembered as one of the most influential Republican donors and for his controversial views on climate change.

Koch left his role at Koch Industries a year ago. At the time USA Today wrote:

Koch officials cited health reasons for the departure but declined to provide details on the nature of his illness. David Koch is a prostate cancer survivor and donated hundreds of millions of dollars to cancer research and medical facilities over the years.

In a letter sent Tuesday morning to Koch Industries’ employees, Charles Koch said his brother first announced his “declining health” in October 2016. 

NBC News writes, “With the billions from their business, the Koch brothers helped to build a massive conservative network of donors for organizations that work to mobilize voters and sway elected officials in support of libertarian-leaning economic policies.

But the Kochs were best known for bankrolling right-wing candidates for House and Senate seats. Plus, The Washington Post writes:

On the state and local levels, Koch money was credited with helping Republicans install majorities in 31 state legislatures by 2018.

Forbes reports his net worth is estimated at $42.4B. While the Koch brothers are known as major conservative donors, they have had a rocky relationship with Donald Trump… and have traded barbs over the years.

On the heels of a new book about the Koch brothers, The New Yorker’s Jane Mayer recently wrote about a new book that explored “the extraordinary behind-the-scenes influence that Charles and David Koch have exerted to cripple government action on climate change:”

If there is any lingering uncertainty that the Koch brothers are the primary sponsors of climate-change doubt in the United States, it ought to be put to rest by the publication of “Kochland: The Secret History of Koch Industries and Corporate Power in America,”