Billionaire businessman David Koch, a major donor to right-wing libertarian causes, has died at the age of 79, leaving behind a complicated legacy.

For nearly eighty years, Koch Industries has stood as the preeminent American business success story, and become one of the country’s largest privately held conglomerates. But David and his brother, Charles, known as the Koch brothers, have also attracted significant controversy — with their business interests and political influence often mingling.

In an interview with Yahoo Finance’s The Final Round in mid-August, before David Koch’s death, “Kochland” author Christopher Leonard untangled this question. He discussed the complex history of the Koch family and its business, which has come to dominate the energy space today.

‘One of the most important companies’ in the U.S.

How, and in what ways, has Koch Industries remained influential in today’s world?

“That’s the question that started the book,” Leonard explains. “You hear about this kind of cartoon character of the Koch brothers as political figures, but in fact, this really is one of the most important companies in the United States. 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 annual revenue of roughly $110 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.

“This company specializes in the kind of stuff that underpins civilization,” Leonard explained. “Fuel, fertilizer, building materials; it really touches everybody’s life.”

The Koch family’s ‘most important resource’

Both Charles and David Koch shared an entrepreneurial spirit, fostered by their father, Fred C. Koch, after whom the company is named. And while this doubtlessly shaped the brothers’ business acumen, it is not their most important resource.

“When you talk about the business and how it became what it is today, this is a company that, back in even the ‘70s and ‘80s, realized the most important resource they dealt with wasn’t gas, or coal, or cattle — it was information,” Leonard said. “This is a company that’s big into trading, and their strategy is to try to know more about the world than their competitors and to trade on that advantage.”

That hunger for information remains a central part of Koch Industries’ business strategy, and often permeates the brothers’ political motivations.