Fans can investigate Sherlock Holmes in Minn.

MINNEAPOLIS (AP) — Anyone searching for clues about the enduring popularity of Sherlock Holmes need not look only to his headquarters on London’s Baker Street.

Deep in an underground cavern at the University of Minnesota lies the world’s largest collection of Holmes memorabilia — a cache sure to expand with material from the new “Sherlock Holmes” movie starring Robert Downey Jr. as the pipe-puffing super sleuth.

To many, it’s a mystery how this trove of tens of thousands of books, toys, games, posters and recordings — from copies of the Holmes stories owned by the last empress of Russia to an original manuscript page of “The Hound of the Baskervilles” — ended up at a Midwestern university, half a world away from the foggy London streets of Holmes and his creator, Sir Arthur Conan Doyle.

The answer is elementary, according to Tim Johnson, curator of special collections and rare books at the University of Minnesota Libraries: A “happy series of accidents” involving a retired university librarian, a Nobel Prize laureate and a Holmes fan who took a “vacuum cleaner” approach to collecting.

“People think the Holmes collection ought to be in London. So it’s ‘Why Minnesota?’ And it’s really just this series of happy events that occurred over time,” Johnson said.

“Sherlock Holmes” was released Christmas Day. Directed by Guy Ritchie (“Lock, Stock and Two Smoking Barrels”), the film stars Downey (“Iron Man”) as a man-of-action Holmes unraveling a nefarious plot by Lord Blackwood in Victorian England with the help of his sidekick Dr. John Watson, played by Jude Law.

The Holmes collection in Minnesota has between 15,000 and 16,000 volumes, and other pieces bring the archive to 60,000 or more, Johnson said. They are kept in a cavern, fitted out for storage, about 85 feet below ground at the Elmer L. Andersen Library, where temperatures and humidity are controlled.

On metal shelves sit memorabilia including magnifying glasses, an ice cream carton with a cartoon cow wearing Holmes’ iconic deerstalker cap and a pillow with an image of Sherlock Hemlock, a Muppet character from “Sesame Street.”

Los Angeles attorney Les Klinger, who wrote “The Annotated Sherlock Holmes” series and was a consultant on the new movie, has donated his papers to the university’s collection. Other major Holmes or Doyle archives are at Harvard University, the Toronto Public Library and Portsmouth, England.

But Klinger calls Minnesota’s collection the “first stop for anybody doing research, because if you’re looking for something, it’s probably in the collection.”

Johnson says he believes retired university librarian E.W. McDiarmid, a Holmes fan, “whispered in the ear” of Johnson’s predecessor that the university should have a collection of first-edition Holmes stories.

The school began amassing the Sherlock Holmes Collections in 1974, buying collector James C. Iraldi’s library of Holmes first editions — 160 volumes and a similar number of periodicals. Four years later, Johnson said, the widow of Mayo Clinic doctor Philip S. Hench donated his Holmes collection.

Hench, who shared the 1950 Nobel Prize in Physiology or Medicine for developing cortisone to treat pain in arthritic patients, had died in 1965. His Holmes collection was 10 times larger than Iraldi’s — about 1,800 books and 1,500 periodicals — and was “full of amazing rarities,” Johnson said.

With the donation of the Hench collection, “the Sherlockian world sat up,” Johnson said. One Holmes fan who visited the university was John Bennett Shaw, a collector from Santa Fe, N.M., who acquired Holmes pop-culture items such as restaurant menus and board games.

“Shaw had the collecting sensibilities of a vacuum cleaner. It was like anything and everything that had to do with Sherlock Holmes, Shaw collected it,” Johnson said.