ST. PAUL, Minn. — Don’t expect the master of ceremonies to get emotional when “A Prairie Home Companion” celebrates its 40th anniversary this weekend.

“I avoid getting choked up. It’s not in good taste,” said Garrison Keillor, humming and snapping his fingers Wednesday as he strolled the Macalester College campus in St. Paul, site of the radio show’s first live broadcast in 1974.

“You never want the audience to be concerned. I coughed during a show in Washington, D.C., recently. People listening at home probably thought, ‘Geez, is this old guy going to croak?’ ”

He returned to Macalester for a festival marking the anniversary with a three-hour live broadcast, a giant singalong, creation of a Lake Wobegon-style “Living Flag” and other hoopla.

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“Prairie Home,” a Minnesota institution that reaches 4 million listeners, has been made into a movie, parodied on “The Simpsons,” graced the cover of Time and earned its creator a Peabody Award. But four decades ago, only a dozen or so people were left in the audience after several people walked out on that first broadcast at Macalester’s Janet Wallace Fine Arts Center.

“It was too fancy for us,” Keillor said. “It was a beautiful little concert hall built for classical music, and we were just this little country-music show.”

Not anymore. An elaborate, giant stage was built for Saturday’s main event.

In many ways, Keillor is approaching the party just like any other show — including that, as of last Wednesday afternoon, he hadn’t gotten around to writing any material.

“You don’t want to do it too far in advance,” said Keillor. “If you do, it’s hard to get serious about it.”

Don’t let his public persona fool you. A work ethic drives the 71-year-old storyteller to spend roughly 16 weeks on the road while also producing books (“The Keillor Reader” is his latest, published in May), running his Common Goods bookstore across the street from Macalester, and developing his first play, expected to premiere in late September.

“If there’s any truth that hard work will get you there, Garrison is the poster boy,” said guitarist Dakota Dave Hull, a regular guest during that first season and among the 50-plus musical acts performing this weekend.

If Keillor is being low-key, the rest of the state is not.

Gov. Mark Dayton declared Sunday “A Prairie Home Companion Day.” Nearly 40 communities, from Ely to Luverne, are calling themselves Lake Wobegon for the weekend.

“There are many of us who believe Minnesota is on the national map because of the persona of our state that Garrison Keillor created,” said Jane Wildung Lanphere, executive director of the Luverne Area Chamber. “Minnesota Nice isn’t just a saying. It is a badge of honor we wear because of the exposure of ‘Prairie Home Companion.’ ”

Keillor remains unfazed by the attention. Perhaps he’s saving up his excitement for a 50th-anniversary bash?

“What an imagination you have,” Keillor said. He has no immediate plans to retire, but doubts he’ll still be at the helm a decade from now. “It wouldn’t be a good idea. You can be a U.S. senator into your 90s — and people have — but it’s not a nice thing to watch up close.”