Oct. 16–The 1920s were in full roar when the Sir Francis Drake Hotel opened in the fall of 1928. It was one of the city's first skyscraper hotels — "26 Stories of Luxury," The Chronicle called it at the time, overestimating its height by five stories.

It came with a grand marble lobby, radios in all 600 guest rooms — and a Prohibition-era hideaway where the select few could enjoy a drink of illegal bootleg Scotch. The room was so secret it was not even included in the hotel's blueprints.

The Kimpton Sir Francis Drake Hotel is celebrating its 90th birthday Thursday with a big party. The party, called "Let's Misbehave," is in the Starlight Room atop the hotel and will feature a '20s theme with jazz and modern music mixed in. The DJs have very un-1920s names — the Known and Limbs Akimbo.

That's a far cry from the hotel's grand opening in 1928, which featured music by classical violinist George L. Lipschultz, listed as the hotel's concertmaster, who led the house orchestra in a selection of string music.

The Roaring Twenties in San Francisco were a mixture of sedate respectability and wild boom times. The city changed completely in the '20s with a whole new skyline. The 32-story Russ Building, the distinctive Pacific Telephone Building south of Market, the classy 450 Sutter office tower and two new skyscraper hotels — the Mark Hopkins atop Nob Hill and the Sir Francis Drake at Powell and Sutter streets — were built within four years of each other and gave San Francisco a distinctive new look.

Then, only a year after the Sir Francis Drake opened, the stock market crashed and that was the end of the boom. No new towers were built for a generation.

But the good times were rolling for sure on Oct. 23, 1928, when Mayor James Rolph, known as "Sunny Jim," opened the Drake's main entrance on Powell Street — and threw away the key. The idea was that the Sir Francis Drake would be such a success that the doors would never close. And they never have.

The papers said 10,000 people came to the hotel's two-day opening event. They marveled at the imported marble in the lobby, the "happy combination of decorations and furnishings," and at 50 floral pieces, including a replica of the Golden Hinde, Sir Francis Drake's ship. There was also an indoor golf course, ice water on tap in every room, dinner, music and dancing.

The new hotel cost $5 million, a fabulous sum in 1928 — about $71 million in today's money.

What the gala throng didn't see was what the hotel now calls its "Prohibition Room" on the mezzanine. It was reached by a special elevator and the doors would open with a special key.

It was designed, said David von Winkler, director of hotel operations, "to circumvent the Prohibition laws." Those in the know could contact a "provider" who could supply Scotch and other illegal beverages direct from bootleggers based in Moss Beach on the San Mateo County coast.

The secret room had peepholes bored in the floor to keep an eye out in case of a raid.

A room at the new Sir Francis Drake cost $3.50 a night. That was a bargain at a time when the once-a-day airplane fight to Los Angeles cost $45, and an overnight voyage to L.A. on the steamships Yale and Harvard sold for $13, berth and meals included.

The hotel has gone through many changes over the years. It got a major overhaul in time for its 50th birthday. It now has 416 guest rooms and advertises itself as a luxury boutique hotel. On Sundays, the Starlight Room hosts a drag brunch, a buffet featuring a bevy of drag queens.

In the 1940s, the hotel converted private rooftop apartments into what was first called the Starlite Roof, a swank nightclub with a panoramic view of the San Francisco skyline. In 1940, the Drake got its first Beefeater doormen, von Winkler said, when the hotel wanted to show support for the British at a time when Britain stood alone against Nazi Germany. Doormen, dressed in the traditional garb of the guards at the Tower of London, have been a distinctive feature of the hotel ever since.

After the war, the Sir Francis Drake employed Bill Elliott, a former RAF pilot, as a doorman. He stayed for 40 years. Now the hotel's living landmark is doorman Tom Sweeney, the city's best-known hotel personality.

Sweeney took on the job "temporarily" 42 years ago and has been there ever since. He even has a plaque on Powell Street attesting to his fame. He claims he's the most photographed man in San Francisco.

"People take 500 to 1,000 pictures of me a day, no kidding," he said. "I've shaken the hand of every president of the United States since 1976, everybody but Trump."

"I'm kind of historic, but when people see the plaque, they think I'm dead," he said. "Tell them I'm not dead."

He'll be on hand for the hotel's big birthday bash, and every other day.

The party is a ticket event, with prices ranging from $25 to $500 for a ringside seat with drinks and entertainment.

Carl Nolte is a San Francisco Chronicle staff writer. Email: cnolte@sfchronicle.com Twitter: @carlnoltesf