Stripped of the sentimental trappings of the show, which he writes almost entirely by himself, Mr. Keillor’s words leap off the page and bite. In an excoriating book review in The New York Times, he called Bernard-Henri Lévy “a French writer with a spatter-paint prose style and the grandiosity of a college sophomore.” Thrice wed — he and his third wife, Jenny Lind Nilsson, a violinist, have a daughter, Maia, who just graduated from high school — he once described marriage as “the deathbed of romance.”

Throughout his career, Mr. Keillor penned columns, stories and books. He wrote regularly for The New Yorker, where he had a desk, until Tina Brown’s arrival as editor in 1992. “The day I heard that she would replace Bob Gottlieb, I packed up my stuff in a couple cardboard boxes and left in a cab and have not looked back,” he said in an email. But it was radio, his Plan B, that came to define his life.

Born in 1942 in Anoka, Minn., Mr. Keillor grew up the third of six children. His family was Plymouth Brethren, a fundamentalist Christian sect that forbade dancing and going to the movies. But Mr. Keillor’s youngest sister, Linda Keillor Berg, said theirs was a happy home, where family members routinely gathered to sing hymns.

“Becoming a star of any kind wasn’t an ambition our parents seeded in any of us,” Ms. Keillor Berg said, but Mr. Keillor could not be contained. In junior high, rather than signing poems with his given name, Gary, he began using the more regal sounding Garrison. It stuck. He went on to write for the local paper, majored in English at the University of Minnesota, and in 1969 took a job at a radio station as a classical music announcer.

There, he began breaking from convention, interspersing Mozart overtures with songs by the Beach Boys and Grateful Dead. One morning, he aired a live predawn show featuring a cowboy singer and a performer who made wine glasses sing. He later asked his boss, Bill Kling, who founded Minnesota Public Radio and also started American Public Media, to weigh in. “I said I thought it was awful, that it was one of the worst ways to wake up I had ever remembered,” Mr. Kling said. “He said, ‘Well, you know, it’s a beginning.’”

Mr. Keillor’s big break came when his short, slyly racy short story about local parents hiring a live-in prostitute for their teenage son fell into the hands of Mr. Angell at The New Yorker. “I thought it was brilliant,” Mr. Angell said. “The nearest thing to E. B. White that had come along.”