ST. PAUL, MINN. -- It was somewhere back in his boyhood, just after his family bought the new picture window, that Garrison Keillor discovered the difference between an audience and a performer. He sat there in the living room, looking out and thinking that he was watching people, until he realized that a crowd had come to see the window and that those people were watching him. He thought a while about just who was watching whom and decided that the people on the outside were the audience because there were simply more of them.

For 13 years, through his wistful public radio show "A Prairie Home Companion," Keillor has devoted himself to blurring the distinction between performer and audience. His gentle voice created an intimate sitting-around-the-kitchen-table atmosphere and made folks feel that just listening to him was the best conversation they'd had all week. Through the news from Lake Wobegon, he welcomed strangers into a place they thought of as his home, and they, in turn, welcomed him into theirs.

Saturday night, Keillor brought "A Prairie Home Companion" to a close with a final broadcast from the World Theater, still playing with the distinction between audience and performer, still trying to let listeners know that the emotion flows both ways.

"I'm going to miss you an awful lot," he told his radio audience of an estimated 4 million. "I'm going to miss you more than you're going to miss me, is the fact of it. See, there's a lot of funnier people around, and a lot of better singers, and you're going to find another show. But you're my only audience. When I leave you, I'm all alone. I don't have any other audience.

"I'm going to Denmark. I don't have an audience in Denmark. I'm not humorous there. I'm a tall, very quiet person who keeps saying the same things over and over 'cause that's all I know."

And after the sentimental 2 1/2-hour show with several on-air encores, he returned for three more encores before the World Theater audience.

"I want you to know I've never believed in brave and cheerful farewells," he began the show by saying. "When I go I want people to throw themselves down on the floor, the dirt, whatever is down there. And I want to hear weeping, howling, and I want people to throw their arms around my ankles and beg me to stay. We've selected music to help you achieve that level of grief."

Sound effects specialist Tom Keith, producer Margaret Moos and volunteer Ray Marklund were among the most senior crew members remaining from a show that debuted before an audience of 12 people and listeners of a dozen Minnesota Public Radio stations on July 6, 1974, in the Janet Wallace Auditorium on the campus of Macalester College here.

"I did the show for adventure and risk," he told fellow humorist and frequent guest Roy Blount Jr., in an interview in the current Minnesota Monthly magazine, "which is, as you know, good for a shy person to do ... Somebody who's so self-conscious as that, there just isn't any comfortable way to get along. You either go into performing or you become a guy who lives at the end of a quarter-mile dirt road in a shack full of old coffee cans and newspapers."

When the show began its national weekly broadcast in May 1980, there were plenty of Minnesotans who feared it would fail, or worse -- that Keillor and his eccentric Wobegonians would make the area the butt of a national joke. They needn't have worried. The show won the prestigious Peabody Award in its first half-season and grew gradually from cult status into a national phenomenon.

"It's almost like a death," said associate producer Helen Edinger of the reality of losing the show. "Some of us are going through a grieving process."

"I think about 2 o'clock next Saturday I'll be saying, 'Well, it's time to get to the theater.' That's the shape of the hole for me," said Kate MacKenzie, a bluegrass singer who also does the voice of Sheila the Christian Jungle Girl in episodes of "Buster the Show Dog," Keillor's weekly serial.

Public radio station managers around the country, one of whom said Keillor leaving public radio would be like Bill Cosby leaving NBC, are hoping a new show, hosted by former "All Things Considered" anchor Noah Adams, will take up some of the slack. Adams' show, still in the planning stages, is scheduled to begin in January.

Meanwhile, the freight train bearing Buster and his friends must be somewhere south of Memphis by now. In Lake Wobegon they've stopped talking about last Wednesday's all-day rain long enough to take up criticizing how the Sons of Knute botched yesterday's Living Flag ceremony. And here in St. Paul, Keillor is preparing to board a plane for his wife Ulla's native Denmark.

In his final monologue, Keillor left listeners on the shore of a mist-shrouded lake, contemplating the Lake Wobegonians, in "a sweet long rain that meant that ... the river will rise and we can push off from shore in our lovely rafts and the water will carry us over the rocks and around the bend ... At last we can see what is around that bend. If I find out first, I'll let you know. If you see them before I do, give them my best and tell them that I think of them. That's the news from Lake Wobegon."

That's the news for now, anyway. In a "Nightline" interview Friday, Keillor said he felt "an obligation" to the people of Lake Wobegon. But he pointed out, "The stories of Lake Wobegon are kind of stuck back in my youth." He said they needed updating.

Lake Wobegon must be changing, as surely as Keillor's real hometown, Anoka, Minn., is changing. A visitor can still find some of the inspiration for Keillor's fictive small town, though once senses that it is disappearing, that a bit more of it vanishes every day.

It had been a quiet afternoon in Herr Schmidt's Inn near Anoka City Hall. The inn has big glass windows, but it looks dark inside just the same. Over in the corner, a young guy with nothing else to do was banging away at the pinball machine. Two guys in plaid shirts were eating cheeseburgers and talking about pike. A retired couple from Minneapolis were finishing up their beers and were heading out to a seed store, so they could lure a better class of bird into their backyard.

Yeah, it was pretty quiet when Herr Schmidt told his wife to poke her head out the door and watch this. Well, he disappeared out the front door, and she poked her head out the back and of course, after a while, people got curious.

See, there was a Tent Sale across the street and when nobody was looking Herr Schmidt went over and sat down on one of the couches and made himself comfortable. "He just sits there on the davenport, waving at me like he's the only one in town who could get away with that," his wife says. And when you leave there is Herr Schmidt sitting in the shade on a davenport that, if his wife is lucky, he won't get too attached to.

Herr Schmidt notwithstanding, the Anoka of Garrison Keillor's youth has just about vanished. "Anoka is an old, staid community," said Arch Pease, who publishes the Anoka County Union and writes a column called Pease Porridge. "It used to be a lumbering town and it was the potato center of the area and many years ago there was a starch factory here, to make starch from the potatoes. There were four sawmills, now there are none."

On the big map on his wall, Community Development Director Bob Kirchner points out where Swede-Town used to be, and Christian Hill, where the Catholic and Lutheran churches stood, and Whiskey Flats, where the Mississippi ferry men drank, and Frog-Town, which is what the French section was called, though not to the faces of the French.

What a visitor sees is a curious mix of bucolic splendor and urban sprawl. The city is cut by the Mississippi and Rum rivers. There are tableaux everywhere you look: boys swimming in the river, freight trains chugging across old bridges, shirtless old men hacking their way around the municipal golf course in the center of town.

But it is also a town where the cemeteries are hemmed in by two major roads, where tract housing and apartment complexes are starting to crowd out older homes with more character, and where the ubiquitous commercial strip development dominates one side of town. If it produces another Garrison Keillor, his will be a different kind of humor based on a different kind of memories.

Mickey's Diner, near the World Theater, is a landmark in St. Paul, and they don't mind letting you know about it. Ask 'em if business is better on a "Prairie Home Companion" Saturday, and they'll tell you, "Business is always good. This is a landmark."

"But yeah," says a waitress named Colleen. "We had people in last week from New York. They liked it. I guess they got a lot of places like this in New York."

She doesn't see what all the Garrison Keillor fuss is about. He's been in a few times, seemed kind of grumpy. Ordered the Special, talked through his teeth. "I am not familiar with his humor," Colleen says. "I guess it's like Volvos and endorsing things with Beatles songs. I guess it's just the hip thing."

One of the regular customers calls Colleen "baby," but she tells him that she doesn't answer when people call her "baby."

Keillor did not exactly burst like a comet across the sky of his hometown. He graduated from high school in 1960, lanky and sensitive-looking, with a one-man sports magazine under his belt. "The Varsity is one of the new publications," the yearbook reads. "Gary Keillor, its editor, did the research, wrote, typed, printed, stapled and sold it. Gary confesses to having discovered that journalism has more problems than his trigonometry textbook."

"Nobody thought that much of him at that time," Arch Pease says. "He was just another fellow. He was not a shining example."

Of course success has changed most people's view of him. "People who didn't know Keillor at all now know him real well," Pease says. "Success breeds that sort of association, you see."

"Prairie Home's" success has prompted locals and tourists as well to search for the places that inspired the Chatterbox Cafe' and Ralph's Pretty Good Grocery. For the record, the show is named after the Prairie Home cemetery in Moorhead, Minn. A former grocer named Ralph Malmberg thinks Ralph's Pretty Good Grocery is named for the store he used to run in Marine on St. Croix. Bob Kirchner says he thinks his brother Jack, who for more than 30 years has run an auto repair business in Anoka, is the inspiration for "PHC's" oldest sponsor, Jack's Auto Repair. "He told me he thinks he even worked on a couple of his family's cars," Kirchner says.

Asked directly, Jack reacts as though he is testifying before Congress. "Is this the guy, he's kind of a comedian type?" he says. "Yeah, I had customers come in and tell me about these statements he's making up and show me the clippings. At this point, I have no knowledge."

He may be the only man around who doesn't have some knowledge of Keillor. "They had him down at the high school, and they had about 2,800 kids down there, and they got them all in the gym and he spoke to them," Pease says. "He got a tremendous reception. The only one I remember getting more of a reception is Hubert Humphrey when he was the vice president. That's good company."

Something in Pease's voice says it's too good company.

"He can sing. He knows where his audience is and he knows how to approach them. Some say it's a great book and some say it isn't. That's not for me to judge."

But did you like it?

"No, not really. I thought it could have been better written. I have a brother-in-law in Illinois, though, he doesn't miss him."

It is getting to be rush hour on St. Francis Boulevard, rush hour being a pretty new thing to the Anoka-Ramsey city line. But the tract housing has sprung up and of course almost nobody lives walking distance from work these days, so about 4:30 it gets pretty busy at the intersection of Industry Road, too busy for a two-lane highway. On the northwest corner, standing with her two kids is a young mother who lives in some of the new tract housing. She is trying to cross the boulevard to get something for the kids to eat at the Food-N-Fuel, but it's just too busy and there is no traffic light. The kids are a girl of about 6 and a boy of about 4. They are not dressed as well as she'd like, but then neither is she. The boy keeps walking around and his mother grabs for his hand and after maybe five minutes of standing there she realizes that they are going to have to make a run for it. At the slightest break in the traffic she makes her move, head down, hauling the kids along, and when she gets to the other side she turns and looks at the traffic. You can still get across the street in Garrison Keillor country, but it sure keeps getting harder.