NEW YORK – Emerson Spartz remembers the good old days. It was Fall 1999, Spartz was 12 and he decided to create a little Web site about a hot new series of fantasy books.

The Harry Potter craze was just beginning.

“The sites were very primitive, especially compared to modern Harry Potter sites. They were amateurishly done,” says Spartz, founder of mugglenet.com, one of the leading Potter sites. “The biggest Web sites were updated a couple times a week at most, and other than message boards, there was no interactivity between fans.”

Like J.K. Rowling herself, Potter fan sites didn’t start out to make history. They popped up like so many variations of “Wayne’s World,” operated on the cheap by “teenage kids out of their basements,” Spartz recalls.

It’s been 10 years since readers met the boy wizard in Rowling’s first book, “Harry Potter and the Sorcerer’s Stone.” More than 300 million copies later, the Potter series ends July 21 when Scholastic Inc. releases the seventh adventure, “Harry Potter and the Deathly Hallows.”

Spartz and his many fellow Webmasters are looking back at their own place on this record-breaking ride. The story of Potter has all along been a story of its fans, and, like everything else about Potter, the fan sites are in a special class, for their size, and for their influence.

“The Potter sites set the standard,” says Anthony Ziccardi, vice president and deputy publisher for rival Pocket Books, an imprint of Simon & Schuster that releases “Star Trek” paperbacks.

“The thing about the Potter phenomenon is that it has a huge, active fan base, both young and old, with a lot of teenagers. The ‘Star Trek’ fan sites are a little bit older – most of the fans are 25 and older. The Potter sites really stand out – they’re like a marketing machine in and of themselves.”

The Potter sites have long advanced from the slow pace, simple texts and dull backgrounds of the early years, and now have all the latest accessories: blogs, podcasts, audio and video. They no longer just comment on the news, but participate. Rowling has praised the sites by name, granted them rare interviews, and even used one site, the Harry Potter Lexicon, to check facts.

Warner Bros., which once tried to shut down many of the fan sites because of copyright concerns, has invited Spartz and others to the sets of Potter films and premieres, valuing their expertise and, of course, their access to so many fans.

“When we have brought representatives from some of the key fan sites and showed them the details for the film sets, even if some of them were disappointed that we had left out certain elements from the books, they respected what we were trying to do,” says Diane Nelson, Warner Bros.’ executive vice president for global brand management.

“We’re not naive enough to think we’re going to avoid criticism, but bringing the fan sites into the process is what we feel is really important.”

Melissa Anelli, the Webmaster for another popular fan site, the-leaky-cauldron.org, has been part of the online Potter world since 2001, not long after Leaky started, “as a means for a few friends to keep track of all the news about Harry Potter.” The first Potter film was coming out, as was the fourth Potter book, so they experimented with a relatively new Web tool: a blog.

“It was a one-page blog, with no other features but news. It had a blue background and Halloween orange text,” recalls the 27-year-old Anelli, a freelance journalist who lives in New York. She is writing a book, tentatively titled “Harry, A History,” about the Potter phenomenon.

“The movie studio didn’t know who we were, and didn’t care. It took a year of relentless e-mails and phone calls before someone took me and my questions seriously, and started giving us reportable information,” Anelli says. “It took even longer for that open atmosphere to spread to the publishers, but the staff of Leaky felt that it was worth pushing for.”

Webmasters themselves learned the value of bringing in fans to the game. Spartz, now a sophomore at the University of Notre Dame, was living in nearby La Porte, Ind., when he started MuggleNet, with the hope of building a database of Potter information. After receiving countless e-mails, Spartz reasoned that the best way to treat his new online friends was to put them to work.

“The site exploded in content and design offerings, and traffic went through the roof,” says Spartz, who now has a staff of 120, virtually all volunteers.

Anelli estimates there are some 3 million to 4 million Potter sites in dozens of languages, including French, Spanish, Russian, Mandarin and Hebrew. Like a small town exploding into a vast metropolis, the Potter boom drove some of the pioneers out, including Mike Gray, an early member of Harry Potter for Grownups, a Web site founded in the late 1990s.

“Somewhere along the line, I noticed that participating in a list with more than 10,000 members didn’t really ring my bell – and that being responsible for people whose bells were thusly rung probably wasn’t my calling. So I slipped off the stage,” Gray says.

Web sites helped start the international Potter obsession and kept it going when Rowling took three years – 2000-2003 – to write Potter V, “Harry Potter and the Order of the Phoenix,” driving fans to tear “their hair out in anticipation,” Anelli recalls. She also cites the first Potter movie, “Harry Potter and the Sorcerer’s Stone,” which came out in 2001.

“That’s when fans needed a stronger visual fix of Potter; they wanted to see more pictures of the celebrities, they wanted to read about them and see clips from the films,” she says. “So, they hit the Web sites – and discovered wellsprings of information for their love of the books, too. They found encyclopedias and games and guides and fan-fiction and fan-art – enough to keep even the most rabid fan sated between novels.”

Potter sites have been counting down to the big night in July and will likely stay around well after Rowling moves on. Two more movies are planned after this summer’s release of “Order of the Phoenix,” and a thriving genre of Potter fan fiction remains, with readers not waiting for “Deathly Hallows” to imagine how they would continue the story.

“We already do have stories like that, called ‘Post-Hogwarts,'” says Jennie Levine, a reference librarian in Baltimore and co-founder of the Potter fan fiction site, www.sugarquill.net.

“We’ve had people doing that since they released ‘Goblet of Fire.’ We call them ‘alternate universe’ stories because we know a lot more now about what happened to the characters.”

“We’ll definitely be around until after the movies come out,” Anelli says. “Whether we follow all of J.K. Rowling’s career or not, we’re not sure. There does come a time when the people currently involved in the site will have to move on with their lives; running it takes a lot of time, effort and energy from everyone involved.

“But no matter what happens, these years will always be among the best in our lives.”