Billionaire philanthropist Peter B. Lewis was well-known for giving millions to colleges and other charities. (Tony Dejak /ASSOCIATED PRESS)

Peter B. Lewis, who shepherded Progressive Corp. from a small-time operation to one of the largest auto insurers in the country, and who became a billionaire philanthropist and backer of marijuana legalization, died Nov. 23 at his home in Coconut Grove, Fla. He was 80.

His philanthropic adviser, Jennifer Frutchy, confirmed the death. Bloomberg News reported that he had a heart attack.

Glenn M. Renwick, Progressive’s president and chief executive, said the company owed its growth and its culture of openness to Mr. Lewis. In 1965, he became chief executive of Progressive, built from the company his father co-founded in 1937. Mr. Lewis held the leadership post for 35 years, during which Progressive — and his fortune — steadily grew. In 2006, Forbes calculated his net worth at $1.4 billion.

The company, based in Mayfield Village, Ohio, was known for its un­or­tho­dox business model of selling insurance polices to drivers who were considered high-risk and who had been rejected by other insurers.

Mr. Lewis used his wealth to support a number of progressive causes, most prominently marijuana law reform. Mr. Lewis — who had used marijuana for pain relief after the amputation of his lower leg — helped bankroll marijuana-related causes in Ohio, Washington state and Massachusetts.

In a 2011 interview with Forbes Magazine, he said he first tried marijuana at age 39. He said he found it to be “better than scotch” and later relied on it for pain management.

“I don’t believe that laws against things that people do regularly, like safe and responsible use of marijuana, make any sense,” Mr. Lewis told Forbes. “Everything that has been done to enforce these laws has had a negative effect, with no results.”

Peter Benjamin Lewis was born Nov. 11, 1933, in Cleveland. He graduated in 1955 from Princeton University. His senior thesis was titled “The Financially Irresponsible Motorist: A Problem in Practical Politics,” according to the Daily Princetonian. He later was a Princeton trustee and donated more than $220 million to the university.

Mr. Lewis also was a trustee of the Guggenheim Museum, but he stepped down in 2005, saying he disagreed with the institution’s focus on international expansion. He had been a leading benefactor of the museum, donating tens of millions of dollars.

Mr. Lewis donated $36.9 million for the construction of a building at the Weatherhead School of Management at Case Western University in Cleveland. The building, which is named for Mr. Lewis, was designed by architect Frank Gehry.

For a time, Mr. Lewis largely stopped giving to Cleveland-area concerns, saying there was little cooperation among civic leaders or public development. Last year, however, he donated $5 million to the Cleveland Institute of Art, the Cleveland Plain Dealer reported. At the time, he said he made the donation because a development plan that impressed him in 2004 had met his expectations.

— From news services and staff reports