The original sign welcoming visitors to Las Vegas on display at the entrance of Las Vegas Boulevard. (AFP)

Las Vegas (Nevada), May 16 (AFP): Las Vegas kicked off its 100th birthday celebration with a “helldorado” party and what organisers claim to be the world’s largest birthday cake.

Some 600 volunteers assembled the cake to organ music in a hangar on the outskirts of the city, after seven semi-trucks hauled in the 43 tonnes of cake and 15.5 tonnes of icing.

“That’s 23 million calories,” Brian Averna, executive chief of Sara Lee Foods Company and leader of the volunteers, said. The cake measures 31 metres long, 15 metres wide and 50 centimetres high.

Organisers expect the Guinness Book of World Records to confirm the record-setting cake within weeks.

But there were no long-legged showgirls or slot machines as the city celebrated its centennial Sunday along a stretch of downtown known as Glitter Gulch.

Instead, Sin City wrapped its neon arms around its less-than-flashy railroad history, remembering how the booming desert metropolis got its start.

Dressed in a cowboy hat and vintage clothes, mayor Oscar Goodman kicked off a mock auction by taking on the persona of former Senator William Clark of Montana, who founded a railroad depot where the city now lies.

On May 15, 1905, an auction was held to bid on 110 acres, or 1,200 lots, to build the town.

An announcement at the time said people could bid on lots ranging from $100 to $750, but “the sale of intoxicating liquors” was prohibited on all but two blocks. That rule didn’t stick around long ? booze is everywhere in modern Vegas.

In the 100 years that followed, people have flocked to Las Vegas for the sunny weather and job opportunities, turning a dusty railroad town into one of the fastest growing cities in the country.

But while the city has witnessed unprecedented growth in the last several decades, not everything has changed with time.

Bob Combs, 65, who came 45 years ago and runs a pig farm, said Las Vegas is still primarily known for its sinful excesses. “Then it was an adult playground,” he said. “People came, had a good time and left.”