Amoeba Music is the only record store Charlotte Parsons has known. The emporium in an old bowling alley on Haight Street opened when she was 6, and right up through high school she was among the masses flipping through the bins of CDs, their plastic cases clacking like the sound of corn in a popper.

Then the clacking stopped. “CDs aren’t part of my life at all. When I went to college, I stopped listening to them,” says Parsons, 26, as she flips through the comparatively silent bins of LPs in cardboard jackets. “Now it is vinyl or Spotify.”

Regulars like her are the reason Amoeba will live to see its 20th anniversary on Wednesday. A $25 sticker price for shrink-wrapped vinyl does not seem to be a barrier, whereas $15 for a CD has always been a rip-off.

New vinyl, which sometimes comes with a download code for online transfer, is in demand and so are those antiquated systems to play it on. Turntables under glass have replaced the listening station for CDs, and the display case of “New Arrival Vinyl” gets the most prominent location.

“It’s a big part of why we’re still in business,” says product manager Tony Green, 58, “The people buying records are not grizzled veterans like us. You see a lot of 25-year-olds.”

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Green was working there on Nov. 15, 1997, the day Amoeba opened. There was a line outside in the morning rain, and when the doors were finally unlocked, shoppers poured down the ramp and into rows and rows of bins. There were 100,000 used CDs and 70,000 new, and it was estimated to be the largest store in America that specialized in used CDs and vinyl.

“You don’t need any money to shop at Amoeba,” says Joe Goldmark, 66, a partner-manager in the San Francisco store. “You can just bring some stuff that you are tired of, trade it in and walk around like a king, buying whatever you want.”

The currency is a credit slip that is embossed, initialed and issued at the long buying counter, manned in the early years by four or five buyers who were as busy as customs agents.

All day long you could stand there and watch people offload all that plastic, stare wide-eyed at the cash figure on that credit slip and leap down the ramp and into the bins. Then they’d leave loaded down with as much plastic as they walked in with.

At its peak in 2001, Amoeba was its own beautiful economy, with an endless flow of rock posters, T-shirts, books and collectibles coming in and out like the tide. On a busy Saturday, 10,000 items came in and 10,000 went out.

Then came Oct. 23, 2001, the day Apple introduced the iPod for downloading any song for 99 cents. That and streaming all but killed the CD, which nobody but the record stores loved or even liked anyway.

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The big box San Francisco retail stores — Tower, Virgin and Wherehouse — all went under. If Amoeba wasn’t the largest record store in the country when it opened, it is by now.

“We’re a different beast than they were,” says Goldmark. “We don’t kowtow to the industry. We don’t put up huge pictures of Madonna. We’re like a large indie store.”

One reason Amoeba is still in business is that the partners own the building, which covers nearly half a block. Another reason is that they have remodeled the upstairs into offices and leased it to a clinic that issues medical marijuana cards. A green line on the floor points the way. It is not a medical marijuana dispensary.

“We use that to help us finance Amoeba these days,” says Goldmark.

Because it is so big and because it has survived, Amoeba has become a tourist destination. If visitors can’t carry vinyl on their return flight they can always carry an Amoeba T-shirt, costing $14.98.

The staff, among whom 10 or 15 have been there from the start, are the entertainers, and some like to encourage the indie store motif. They move among the rows as though they are actors in “High Fidelity,” the 2000 film that glorified a shop called Championship Vinyl and its staff of cerebral, if surly, misfits.

One guy dressed in black even looks like Jack Black. When a customer presumes to ask, “Do you work here?” he answers, “yeah,” and keeps on moving.

For someone who hasn’t been there in a while, one question is what happened to the jazz room, a highly touted selection of 10,000 CDs that had its own room when the store opened. Now that area is for video.

“DVD’s and Blu-rays helped a lot for a while,” Goldmark says, “but that is shrinking.”

Nothing has shrunk like CDs. The main floor used to be evenly divided into new and used, on either side of the center aisle. Now there aren’t enough used CDs to merit their own section and new CDs don’t sell enough to stock in quantity. So new and used are mixed together, with the rest of the space given over to vinyl.

It may be only one-third of the floor , but on this day, this is where three-quarters of the shoppers are. Among them is José Lopez, 35, a Mexico City economist en route to a $200 spree.

“Every time I come here to California, I come to this store,” he says. “There is nothing like this anywhere. Not in New York. Not in Europe.” His basket contains both Tom Petty’s “Southern Accents” and a symphony by Mahler. It also contains both vinyl and plastic. “They are missing a couple of LPs,” he explains. “That’s why I am buying CDs.”

Lopez might want to plan a trip for the 20th anniversary weekend. In addition to a free in-store concert by the Cuban-Parisian twin sisters Ibeyi, there will be a rollout of 1,000 vinyl records that have been deemed collectible and hoarded for the anniversary.

This should please Parsons, who shops on her day off as manager of Patrick Evans Salon on Grant Avenue.

“I really like to listen to an entire album all the way through,” she says, while loading in new copies of “She & Him” and “Ella Fitzgerald Sings the Cole Porter Songbook,” total cost $55.

By the 25th anniversary, Goldmark expects the store to be half vinyl. He also expects CDs to hang on as stubbornly as vinyl did when it was declared dead 25 years ago.

It might even make a comeback. The commercial cassette has.

When Amoeba opened, tapes were up on a wall like museum pieces in their little plastic cases with miniature album covers. They languished there until two years ago, when people started asking for them for “no good reason other than nostalgia,” Goldmark says.

They are now off the wall and in racks, 4,000 of them new and used, from $1.99 to $9.99. Heavy metal is a favorite.

“They are actually selling,” says Goldmark. “I’m always amazed.”

Sam Whiting is a San Francisco Chronicle staff writer. Email: swhiting@sfchronicle.com Instagram: @sfchronicle_art

Video: Tony Green describes the Amoeba vinyl revival at http://bit.ly/2zK2lW3.

20th anniversary party: Ibeyi will play a free in-store concert at 5 p.m. Friday. All-day action will start at 10:45 a.m. Saturday with a New Orleans-style neighborhood procession led by Blue Bone Express. 1855 Haight St. (415) 831-1200. amoeba.com