Bethel, N.Y.,-- There must be ghosts here, singing in the hills and swimming naked in Fillipini Pond. Down on the alfalfa field that Max Yasgur used to own, they gather every day, 400,000 strong. They park their cars in the middle of the road, eat peanut butter and jelly for dinner, smoke cannabis for dessert.

Yes, there must be ghosts here, those that frighten and those that cheer. Why else would so many people still be both angry and amazed?

Fifteen years ago this week, as the miasma of Vietnam worsened, legions of the young made their way to this Sullivan County hamlet for a music festival billed by its promoters as "three days of peace and love:

When the Woodstock generation departed, however, it left behind a town in turmoil. Now, the old grudges and fears have re-emerged. People are once again muttering obscenities about the "long hairs" and the "Communists" as if they were still here haunting the place or, worse yet, as if they might return.

Bert Feldman, a short, unthreatening 62-uear-old man who totes a thick walking stick to spell an injured back, started the whole thing.

A former editor of a weekly newspaper, his passion is local history. For three days in August 1969, he worked as a security marshal and guide at the festival, The historian as participant.

Like others here, he at first opposed the gathering, but once a part of it, he came to believe that Woodstock was "a singular event in American social history," one that "crystalized a generation."

Thus converted, he decided to mark the 15th anniversary of the festival by erecting a monument on the site. The festival was originally to be held in the town of Woodstock, 50 miles to the north, but at the 11th hour, official opposition forced a change of site.

In Mr. Feldman's mind, this "holy ground" carries the same import as the battlefield at Gettysburg. The analogy, which he offers to anyone who will listen, does not sit well with some of his neighbors.

"Gettysburg?" said George Neuhaus, the Town Supervisor.

"No, it's a disservice to Gettysburg and what that stood for. The festival was more like the Chicago fire. Do they have markers commemorating that one?"

His derision aside, his comparison might be more apt than Mr. Feldman's. Almost without warning, Bethel was consumed. The flower children came like a firestorm. They swept out of the tree lines across the fields. When traffic backed up, they abandoned their cars in the roads -- six, seven and eight abreast, from culvert to culvert, mile after mile. They invaded the stores and bought the shelves clean. For three days in August, tiny Bethel, permanent population 3,500, became one of the largest cities in the state.

"We were lucky it wasn't a complete disaster," said Mr. Neuhaus. "The majority of people don't want a repeat and wished it hadn't happened."

The site of the festival was a wide, sloping field that formed a natural amphitheater on a dairy farm owned by Max Yasgur, an amiable man who died in 1973.

In the years that followed, the land changed hands several times. The stage site and field--some 40 acres--are now owned by Louis Nicky, the 59-year-old proprietor of Ace Auto Glass on Utica Avenue in Brooklyn. He has no plans for the land, but he has given Mr. Feldman permission to put up the monument.

The flavor of the town has changed some in the last decade and a half. In the summer, the dairy and horse farmers share their domain with Hasidim from New York City who vacation in several bungalow colonies here.

It has been a relatively uneventful summer. A rodeo opened in town and people are talking about that. The council also gave its okay to a group that holds war games with pistols that fire pellets filled with dye. And someone caught a big bullhead this year, 21 pounds, 9 ounces. "Darndest fish you ever saw," said the co-owner of the general store.

Now and then, strangers stop in town and ask directions to the site of the festival. They are told to go past the post office and fire station and the small park planted with red and white annuals, past White Lake and along West Shore Road, a narrow stretch that dips and rises, then on for a mile or so until on the left they see a field that sweeps up perhaps a quarter of a mile to its crest.

Off to the side are the concrete foundations of the stage, almost covered now by a stand of wild sumac. The field, as chance would have it, has been recently mowed, as if someone were expecting a large assembly.

Donald Clark, building inspector then and now, can almost see them sitting there. "It was just a sea of humanity," he said. "It was miraculous, but it tore the town apart. People are afraid a monument will attract them back."

In a corner of the field, where West Shore Road crosses Hurd road, is a small stand of corn. Bert Feldman and Arthur Schubert were there the other day watching Wayne Saward dig a trench in the red shale and preparing a frame for a concrete base.

Mr. Saward, a welder on the Tapanzee Bridge, has joined forces with Mr. Feldman and Mr. Schubert, a Grossinger waiter and alumnus of the Woodstock security force, to erect the small monument -- a cast iron sculpture fashioned by Mr. Saward and a 3-by-4-foot plaque that reads, "Site of the Woodstock Music and Arts Fair, August 15, 16 and 17, 1969."

The day after the foundation was dug, the monument committee came into conflict with town officials over permits and a local sign ordinance. There was some question about whether the monument would be up in time for the festival's 15th anniversary. As in all such disputes, a lawyer was summoned. At 27, Mr. Saward was too young to have attended the festival, but he has been swept up by its mystique and halcyon vision.

"I've read all the books," he said. "I've been here every year on the anniversary. My brother has promised that if anything happens to me, this monument will be taken care of."

"The Mecca concept," Mr. Feldman chimed in, "is not that farfetched."

There are some here who long ago would have welcomed a shrine. "We had a billion dollars worth of advertising," said Art Vassmer, "and we threw it all away."

Mr. Vassmer and his brother, Fred, own Vassmer's General Store--groceries, merchandise, bait and tackle.

During the festival, there were queues at their doors.

They would let them in 40 or 50 at a time. The brothers would have stayed open 24 hours a day, but they just "plain tired out" and had to close for a while.< P>"I'll tell you something," said Art Vassmer, adjusting his white apron, "we cashed I don't know how many checks and you know what, not one of them bounced."

"I'm glad I saw it," Fred said. "It gave me a new experience in life. I always said I never met a man I couldn't shake hands with."

After the festival, some of the businessmen in town organized a testimonial dinner for Max Yasgur. It was a sellout.

Max, as they remember, was proud of most of his neighbors and ashamed of a few. He just could not understand how some people would actually sell a glass of water to a bunch of thirsty kids.

Ken Van Loan was at the dinner. He owns Ken's Garage up the hill from the firehouse and was the president of the local businessman's association.

The other day, as Bert Feldman and his cohorts worked on the monument, gas. [typo?]

"Even with all those cars in town, I never heard a horn blow the whole time," he said. "But let the church crowd get out on sunday now, and they're leaning on their horns. If there had been half a million adults here instead of half a million kids, there would have been a riot."

A few years ago, a car pulled up to the pumps and the driver asked Ken Van Loan if he had been around when the festival took place.

"I been here for 30 years," he answered.

"I was at the festival, too," the man said, "and I owe you for a quart of oil."

And then he paid his longstanding debt.

"That," said the service-station owner, "was the last unpaid bill from Woodstock."

Yes, there must be ghosts here. Why else would Ken Van Loan, Art and Fred Vassmer, Bert Feldman and their kind think so fondly of 400,000 strangers.