LAS VEGAS — In one room, a ghastly photo wall of bloody, uncensored images showcases the mob’s greatest hits.

In another, visitors are taught to load a revolver. And for when a gun just won’t do, a collection of household items — a shovel, a hammer, a baseball bat and an icepick — shows the creative side of some of America’s most notorious killers.

On the 83rd anniversary of the St. Valentine’s Day Massacre, Sin City honored one of its earliest relationships with the grand opening of a museum dedicated to the mobsters who made this desert town. There were tommy guns, money stacks and a bullet-riddled brick wall from the 1929 massacre that saw Al Capone seize control of the Chicago mob.

Las Vegas has long been enamored with its gangster roots. Its longtime former mayor played himself in the mob flick “Casino,” and hotels here often promote their nefarious origins. But even the local FBI agents are in on the publicly funded, $42 million Mob Museum.

“We wanted to make sure the truth came out,” said Ellen Knowlton, a former special agent in Las Vegas brought on to legitimize the downtown attraction.

It’s the second mob-themed attraction to open in Las Vegas in the past year. The Mob Experience at the Tropicana casino quickly shut down because of slow ticket sales and other problems. It’s slated to reopen later this year.

City officials said their version will perform better because it’s an authentic examination of the decisions and circumstances that made Las Vegas an international symbol of debauchery and excess. The museum is housed in an old federal courthouse where the seventh of 14 U.S. Senate hearings on organized crime was held in the 1950s. The proceedings, watched by 30 million people, introduced the mob to most Americans.

But critics argue that the government-backed attraction is a waste of tax dollars at a time when Nevada tops the nation in foreclosures and joblessness.

“It’s a risky bet,” said Andy Matthews, president of the conservative Nevada Policy Research Institute, which protested the museum during its grand opening ceremony Tuesday.

Nevadans and mobsters have a long, storied history.

Casino workers and longtime visitors are known to wax nostalgic about the days when mob bosses kept drink prices low and streets violence-free. Their casinos became celebrity playgrounds and architectural icons. The Stardust, El Cortez, Tropicana, Dunes Hotel, Desert Inn, Flamingo and Fremont hotel were all backed by the mob at one point. Elvis and Priscilla Presley tied the knot at the mob-controlled Aladdin resort.

More recently, Las Vegans thrice made former mob attorney Oscar Goodman their mayor. And when he was term-limited from running again last year, they gave the job to his wife.

The mob, the story goes, helped build out the remote highway that became the Las Vegas Strip. Gangsters took over resorts built by front men, skimmed the profits and built nightclubs, country clubs, housing tracts and malls.

Increased law enforcement scrutiny and competition from business titans like Howard Hughes saw Las Vegas turn corporate in the late 1960s. Then the celebrity chefs and Cirque du Soleil dancers moved in. These days, Las Vegas feels more like a raunchy version of Disney World than a mob hangout.

“We felt nostalgic the moment the old days ended,” said Michael Green, a history professor at the College of Southern Nevada in Las Vegas who is working with the museum.

Museum officials deny that they are sensationalizing the mob experience to sell tickets, which cost up to $18 each. One exhibit shows the modern reach of organized crime through the drug cartels of Mexico, money laundering schemes in the Bahamas, counterfeit rings in China and human trafficking in Brazil.

The museum also tries to show the personal motivations behind the mug shots. There are pictures of a baby-faced Anthony Spilotro marking his First Communion, Frank Costello relaxing in a hammock at home and gambling titan Meyer Lansky with his daughter at the Wailing Wall in Jerusalem. All three were among the mob’s most powerful men.

But the museum’s extensive photography collection depicting cratered heads, imploded cars and full body bags likely will be its biggest draw among fans expecting a hefty dose of mob violence.