Everyone knows "Heidi." The story of the plucky child of the Alpine meadows, her pipe-smoking, taciturn grandfather and her friend Peter the goatherd is famous the world over: It's estimated that 40 million copies of this much-beloved juvenile classic stand on bookshelves all around the world.

But details about the book's author, Johanna Spyri, remain curiously vague to the world at large. Even in her native Switzerland, Spyri is a relatively obscure person. Ask in Geneva, Zurich, Basel or Bern, "Where was Spyri born? Where did she live?" Chances are you'll be told, "I don't really know."

In fact, Spyri's roots are easy to trace. It's less than an hour's train ride east and slightly south from Zurich to Horgen, the town nearest her birthplace in north central Switzerland.

From the port side of the train, through stands of poplar and fir, the Zurich See slips in and out of view. Its shores are dotted with the masts of small sailboats, moored to the docks of the houses that rim this mountain lake. The far horizon is a majestic backdrop of snowy peaks.

At the Horgen railroad station we board a bright red postal bus and make our way up the steep, switchback road. The town's walled gardens and well-swept pavements soon give way to open farmland. Beside every steeply roofed farmhouse is an enormous and meticulously stacked woodpile, testimony that the comforts of steam heat don't extend past town limits. Herds of black and white cows graze the pastures, and we can hear the casual clanging of their bells from inside the bus.

At the hilltop crossroad, there is no post office, no general store. Apart from the bus stop sign and the driver's friendly reminder, there is nothing to tell a stranger that this is the heart of Hirzel, the village where, in 1827, Johanna Heusser was born.

The road is steep, the scattered houses snug and sturdy. Spyri's childhood home is located 200 yards up the hillside. Except for a new wing, it looks very much as it did when Dr. and Frau Johann Jakob Heusser lived there with their six children (Johanna was the fourth).

Johann Jakob Huesser was the only physician for miles around, and his services were much in demand. There was no clinic or hospital nearby; the Heussers' roomy, three-story house was constantly filled with patients, many of whom stayed on as convalescents until they recovered.

Frau Heusser's father was pastor of the Church of Hirzel. Like most churches in northern Switzerland, it's of the Zvingli Protestant sect. It still stands, just across the road from the bus stop. Although refurbished a few years ago, in size and style it remains essentially unchanged. The clear mountain light pours in through the clear glass panes, revealing a simple, unadorned interior.

The pastor's house, also essentially unchanged from the days when the six Heusser children and their parents crowded into its parlor to celebrate holidays with their grandfather, stands just beside the church.

It's only a few steps down the road from the church to the village school. The log and daub structure, built in 1660 and used in the 1830s as a grammar school by the children of Hirzel, fell into disuse after World War II. But in 1980 it was converted into a museum honoring Johanna Huesser Spyri, who studied here until age 14.

The house is entered at ground level, from the back. The whitewashed walls of the small lower room are hung with photographs of the Heusser family.

In one corner, against a hand-painted backdrop of Alpine peaks, is a lifelike tableau. A 10-inch, papier-ma~che' grandfather sits in a chair, outside a log cabin built of sticks. His gray wool beard hangs to his knees; his pipe is long-stemmed, in the true Alpine fashion. Dark-haired, dirndled Heidi pets a goat. Peter, crook in hand, sits cross-legged and barefoot amid papier-ma~che' wildflowers. Pale, frail Klara sits nearby.

Upstairs is Johanna's childhood dollhouse, and a glass-fronted bookcase with 22 first editions of the famous book, first published in 1889 by F.A. Perthes in Gotha, Germany. Its title was "Heidi ... Mountains and Marvels."

From the windows of Johanna Spyri's schoolroom -- as indeed from all the southwest windows of Hirzel -- the sky is filled with the snow-capped peaks of Rigi, Pilatus and the ridges above the Canton of Zug.

In 1852 Johanna Heussel married John Bernard Spyri, a Zurich lawyer and publisher. He was 31, Johanna 25.

A portrait of the bride -- stylishly dressed, as was then the custom, in black velvet, a red print Indian shawl across her arm -- hangs amid other family pictures at the museum. Her wide dark eyes gaze straight into the camera. It's a serious portrait, as befits the occasion, but an undeniable expression around the mouth promises merriment and good humor.

The couple lived in Zurich and had a son, Bernhard. He died when he was 29; just a few months later, his father died.

Johanna Spyri died in 1901, at the age of 74. She published 49 works, all intended for children, all reflecting the carefree joy of simple mountain living.

Only "Heidi" remains in print.

The small museum in Hirzel is open Sunday, 2 p.m. to 4 p.m. However, it can be visited at other times if an appointment is made a day or two in advance by calling its curator, Lydia Hottinger, 729-93-78. Admission is one franc. Hirzel has one small inn, the Morganthal, located a five-minute walk down the hill from the museum.

Linda McK. Stewart is a free-lance writer living in New York City.