Keillor was born on August 7, 1942, to a railway mail clerk and carpenter father and a homemaker mother in Anoka, Minnesota. He later graduated from the University of Minnesota where he had started broadcasting on the student radio station. His career as a radio personality thus began. After the university, he worked as an announcer at KUOM-Radio before hosting The Morning Program on what is now MPR, Minnesota Public Radio. Trying his hand at writing, Keillor also submitted fictional pieces to The New Yorker. Having been raised a fundamentalist Christian, then turning to Lutherism, and now settling with being an Episcopalian, his religious affiliations and his Midwestern roots provide constant material for his radio programs and his writings.
Keillor's big break came when MPR agreed to do a variety show in front of a live audience on Saturday nights. A Prairie Home Companion was born. Keillor brought in musicians, encouraged comic skits, featured satirical commercials, and aired parodies. Rounding out the program, Keillor gave a monologue about an imaginary town and called the idea The News from Lake Wobegon. The radio show ran from 1974 to 1987 when Keillor ended it to work on another program. However, in 1993 he returned to producing A Prairie Home Companion.
Keillor's written many newspaper and magazine articles. He's even penned books for adults and children. A couple of those for kids include Lake Wobegon Summer 1956 and Daddy's Girl. Keillor also writes introductions, as for example, in the Complete Peanuts Volume 1. A versatile man, Keillor has written for Salon.com, appeared in the movie version of A Prairie Home Companion, which he wrote, and penned Homegrown Democrat, a collection of political essays. For Honda UK, Keillor's voice speaks the tagline for their commercials. Keillor can also be recognized as the voice of Odin in Hercules as well as in various recordings and narrations.
In 2006 Keillor opened his own bookstore called Common Good Books in St. Paul, Minnesota. He and his third spouse, a violinist, raise their daughter from both St. Paul and New York City, while Keillor continues writing and hosting his radio program.