The Fillmore West lasted just three years, and Larry Mansbach saw just three shows there. He’s fuzzy on specifics, like which bands he saw, but he is clear on the significance of San Francisco’s most important rock venue during the crucial years of 1968-71, and he’s about to fight for it.

The two-story triangular building that housed the open-floor concert hall above an auto dealership where South Van Ness meets Market Street is facing demolition to make way for up to 984 units in one or two tall, mixed-use towers. The first public hearing before the Planning Commission is Thursday, Dec. 6.

There’s a public notice in the window of the closed Honda dealership, but it makes no mention of the Fillmore West or its predecessor, the Carousel Ballroom. It only mentions “demolition of an historical resource.”

Mansbach knows exactly what that means.

“The Fillmore West is part of San Francisco’s cultural history, and we are losing too much of it,” he said, pounding a fist on a conference table at his real estate office in the historic Hobart Building on Market Street.

Mansbach has the backing of a 78-page report compiled for the city as part of the draft environmental impact report, which the Planning Commission will consider Thursday. It declares the Fillmore West to be eligible for the California Register of Historic Resources.

“This is San Francisco, 1968. This is a disappearing species,” said architectural historian Debi Howell-Ardila, who compiled the report for SWCA Consulting. “It would be great if they could somehow keep the Fillmore West.”

The Planning Commission and the Board of Supervisors cannot ignore the finding. The Historic Preservation Commission recommends an interpretive program, which could be as simple as a historic plaque on the new building or a website explaining the legacy of the concert hall, which hosted such rock luminaries of the day as Led Zeppelin, Creedence Clearwater Revival and Sly and the Family Stone.

Jim Abrams, attorney for developer Crescent Heights, said there are plans to honor the site. But to Mansbach, nothing will do short of preserving the Fillmore West, which is still intact and was leased earlier this year to NPU Inc., a venue management company.

The company cleaned up 40 years of motor oil and now rents out the hall as an event space called SVN West. Mansbach wants the second-floor space incorporated into the new towers, an idea the developer says is impossible.

“I’m getting fed up with San Francisco history being demolished by the highest bidder,” Mansbach said.

There is much confusion about the Fillmore West, owing largely to the fact that it is not on Fillmore Street, not in the Fillmore district and not the same place as the flourishing Fillmore music hall on the corner of Geary Boulevard.

When the “San Francisco Sound” took hold in the mid-1960s, the two large concert venues were the Fillmore Auditorium, run by Bill Graham, and the Avalon Ballroom, run by Chet Helms. The Avalon, at Van Ness and Sutter, held about 500 and the Fillmore about 1,300.

There was a third venue, an upstairs dance hall from the swing era originally named El Patio — “the Ballroom of Distinction” — and later changed to the Carousel Ballroom. It had a capacity of 1,500 and was sitting vacant. So the Big Four of San Francisco bands — Grateful Dead, Jefferson Airplane, Quicksilver Messenger Service and Big Brother & the Holding Company — came together to open their own concert hall.

“It was a complete hippie outfit. You could use barter to get in,” said rock historian Joel Selvin, who has written many books about the scene. “It was also a slap in Bill Graham’s face.”

The Carousel didn’t last a year before Graham took over the lease. His first show, the Paul Butterfield Blues Band and Ten Years After, was on July 2, 1968. Once Graham opened the Carousel, he closed the Fillmore Auditorium and soon changed the name of his new club to the Fillmore West, a reference his other club, the Fillmore East, which he’d opened just three months before, in New York City.

Mansbach is certain that he saw the Grateful Dead at the Fillmore West, and it’s a good guess because the city’s house band played there something like 65 times.

But he missed Big Brother & the Holding Company’s final San Francisco show with its soon-to-be-departed singer Janis Joplin there. He also wasn’t there to see the Who perform the rock opera “Tommy” or to see Santana, Aretha Franklin or Miles Davis, who all made live albums in the room.

“The albums were recorded there because the Fillmore West had a worldwide reputation as the most important stage in the rock world,” Selvin said.

The place had decorative arches and an open wooden floor that doubled as a basketball court. No alcohol was served, and the cover charge was usually $3 or $5.

During its glory days, Mansbach was in school at George Washington High in the Richmond and wasn’t able to attend shows until he was a freshman living in the dorms at UC Berkeley, in 1971.

“I only caught it at the end, because there was an age issue,” he said.

By then, the building had been sold and was slated to be redeveloped into a 400-room Howard Johnson’s motor inn. Graham found a larger space at a ground-floor ice skating rink called Winterland Ballroom in what is now called Lower Pacific Heights. Graham had already been putting on shows there, but then he made it the center of his weekend operations.

It had a balcony with fixed seating all the way around and was three times the capacity of the Fillmore West, which Graham closed with an epic four-night flourish leading up to the Fourth of July, 1971.

It became a boxed set LP called “Fillmore: the Last Days,” and a documentary film. There is footage of Graham on the phone with band managers explaining why he was closing.

“I want it my way, and that’s why I am getting my f— ass out of here,” he shouted into the mouthpiece. “I’ve had to put up with too much for too long. Why do you think I want out? Because these groups have gotten too authoritarian.”

To make his point, Graham closed the Fillmore East simultaneously.

Winterland closed after a televised all-night show by the Dead and the Blues Brothers, with John Belushi and Dan Aykroyd, on New Year’s Eve 1978. It was leveled for apartments, and the only tribute was a restaurant named Winterland, which wasn’t even on the same site.

To Mansbach, that remains a travesty and an embarrassment, and he doesn’t want to see the Fillmore West vanish the same way.

“San Francisco was the international capital of music,” he said. “It is known wherever I travel, even now.”

Mansbach said he was a staff planner with the city Planning Department from 1977 to 1980 and that one of his old colleagues slipped him the historical report on the Fillmore West building, which was prepared in September 2016.

“I saw the address ‘10 South Van Ness’ and was shocked,” he said. Mansbach read the report, then cleared his calendar for 1 p.m. Thursday to be in the Planning Commission chambers at City Hall.

“This project, which is going to add hundreds of housing units, is a good project,” he said. “I’m going to testify that it incorporate the preservation of the Fillmore West.”