In an unprepossessing, two-story stucco garage and office building at the eastern foot of Telegraph Avenue here, a young inventor, Philo T. Farnsworth, transmitted the first television picture in the United States on Sept. 7, 1927.

The building does not look like much today. It is not on any Gray Line bus tours, and most people are not even aware of its existence, let alone its place in history.

But an action by the San Francisco Board of Supervisors earlier this month denying historical landmark status for the building has touched off a controversy about its place in contemporary American history and about the city's commitment to historical preservation.

The supervisors, according to an aide to the board chairman, John Molinari, acted on a recommendation of the city's Historic Preservation Board that the building, at 202 Green St., not receive landmark designation because its interior bears almost no resemblance to the building as it was when Farnsworth worked there.

"It's not as if you could go there and see the lab where television was invented," she said.

And Robert V. Guiste, the building's present owner, objected to landmark status because it would prohibit him from making any architectural changes or eventually tearing the building down to make way for new construction.

"I'm for history," he said in an interview, "but the building has been changed. It's not the building that was there years ago. We're being asked to rewrite history."

Landmark status was supported, however, by the Northern California Motion Picture and Television Coordinating Council. And local television columnist Terrence O'Flaherty accused the supervisors of being "appallingly shortsighted" and an embarrassment to the city.

"I doubt that there is a city on earth that would not welcome the honor of inventing the most important communications machine in the history of the world," he said. "It appeared to many observers that the opposing supervisors were mor strongly influenced by the pressures brought by the present owners of the building than the historical enhancement of the city that they serve."

Guiste said he has placed two bronze plaques on the building at the request of historians to commemorate Farnsworth's work there, but both of them subsequently were stolen. He said he planned to put up a third plaque.

Farnsworth, who died in 1971 at 64, conceived the basic features of today's electronic television system in 1921 when he was a high school student in Idaho. Five years later, with the backing of a group of California investors, he came to San Francisco and set to work in a large, skylighted loft at the Green Street address to refine his system.

A year later, he had perfected an "image dissection tube" to the point that he slipped a glass slide with a heavy, straight line across it into place and watched with his wife, his brother-in-law and several laboratory assistants as the image was transmitted to a receiver. Thus was primitive television born in the United States.

At the time of his death, he had 165 basic television patents on everything from the image dissector to such features as scanning, synchronizing, focusing, contrast, controls and power. His first patent for an electronic television system was issued in 1927.

A recent visitor to the building found offices for architects and designers occupying most of the second floor. The first floor is a combination warehouse and garage. A secretary said she knew of nothing in the building to commemorate Farnsworth's accomplishment except "a clipping about him hanging in the kitchen."