The address looks like many in modern South Boston: a sleek, multiunit residential building that could easily be home to the young professionals who now live in the once white, working-class neighborhood.

From the front of the building, an inflatable bouncy castle can be seen out back. Children and parents are milling about.

In the road, behind the wheel of his Boston Detective Tours trolley, Joe Leeman is explaining the property’s gruesome history: A trio of notorious gangster James “Whitey’’ Bulger’s victims were buried in the home’s dirt basement — Arthur “Bucky’’ Barrett, John McIntyre, and Deborah Hussey.

“He dragged three individuals in there,’’ he told the crowd.

Over the course of an hour-and-half tour, Leeman, a retired Boston police lieutenant, narrates a mix of revolutionary history you learn in school with chronicles of the city’s underworld. Think Bunker Hill, Samuel Adams, and the Boston Tea Party combined with the Irish Gang War of the 1960s, the Italian mob’s past presence in the North End, the Boston Strangler murders, and, yes, “Whitey’’ Bulger.

Leeman — and other Boston crime tour companies — is trying to stake out his own grisly corner of a billion dollar tourism market that, even given a COVID-19 pandemic hangover, is still big business.

Last year, according to state estimates, the city welcomed about 10 million domestic travelers who spent nearly $9.7 billion and generated $600 million in state and local taxes.

To separate himself from the competition, Leeman leans into his own experience working for the police and growing up in Boston.

He is an affable and self-deprecating presence behind the wheel, delivering — in his rapid-fire Charlestown accent, of course — personal vignettes about growing up in the city and working on its police force for a quarter century.

“It was a crazy, crazy time,’’ he said of his youth growing up halfway up the hill on Auburn Street.

He describes the tour as “60 percent crime, 40 percent history.’’ He doesn’t want to be “all doom and gloom’’ even though he acknowledges some customers often lobby for more blood and guts.

“I really enjoy history,’’ he said. “I just find it so interesting that this country was built right here, right in Boston.’’

The seeds of the tour were sown years ago. During a 2004 trip to London to visit one of his sons, he took a Jack the Ripper walking tour and found the experience incredible, he said. And when he was a Boston police officer, local judges would have him take interns on a tour of Boston — specifically, he said, “some gritty places, some tough places.’’

“As I’m driving I would be thinking, ‘I could do something like this,’’’ he said.

Banking on consumer interest in Boston’s often macabre history is not a new idea.

Tom Collins owns Mobsters and Lobsters, a tour company with a similar schtick that covers some of the same ground: the old North End haunts of the Italian mafia, the infamous Brinks robbery, Whitey, the Boston Strangler. Perhaps the biggest difference, though, is that tour ends with a lobster dinner at Venezia in Dorchester.

Collins’s tour company has been around for about a decade and only does corporate events and pre-booked group outings — no public tours. There are currently two trolleys, and Collins estimates his company does more than 400 tours annually.

Collins, a 56-year-old former movie prop maker, admits to considering a life of crime during his South Boston boyhood. But he was deterred by the fact that he didn’t want to die and didn’t want to go to prison.

“Those are the things that usually happen to gangsters,’’ he said.

For him, the allure of the grittier chapters of Boston history is simple: Who doesn’t like crime stories?

“It’s fascinating stuff, and it’s history,’’ he said, adding that many Americans are already familiar with the Revolutionary War aspects of the city’s story.

While growing in popularity, tours like Collins’s and Leeman’s pale in comparison to the likes of a company such as Boston Duck Tours, which was established in 1994 and currently has 28 vehicles. The company estimates that more than 460,000 people took one of its tours last year.

Leeman is starting small. He has one trolley and one employee — himself. He does the driving and the talking. His narration is constant and quick. And he is a fount of information about modern and historical Boston.

There are references to townies and toonies — people who grew up in Charlestown and those who moved there later. He speaks of a time when bank robbers preferred Jeep Cherokees for getaway cars because of the vehicle’s ability to hop curbs. He even plays the 911 call of Charles Stuart, who killed his wife and attempted to pin the blame on an unidentified black gunman, a story many in Boston believed until Stuart jumped to his death off the Tobin Bridge, shortly after his younger brother identified him as the real killer.

There’s the video of Italian anarchists Nicola Sacco and Bartolomeo Vanzetti, talks of Paul Revere’s forensic dentistry abilities, and an explanation of how the deadly 1942 Cocoanut Grove fire changed local fire codes.

He passes a defunct Charlestown tavern that was the backdrop to a fatal shooting decades ago.

“There was 29 people that came out of the bar, they interviewed all 29 people,’’ he explained. “And all 29 people stated they were in the bathroom at the time of the shooting.’’

Then, the punchline: “The only problem was it was a one-stall bathroom.’’

In Charlestown, he stops the trolley. He has two fake hips and needs to stretch, he says. He shares a story about tackling a masked bank robber while he was working a detail. He drove up on the sidewalk to apprehend the suspect, while another cop was chasing the suspect at gunpoint.

“My heart was going a mile a minute,’’ he said.

In the North End, he shows a photo of a man covered in blood. The violence had its genesis in a road rage incident that spiraled out of control. The man in the photo was grazed in the neck by a bullet.

“It was really easy to catch him, because I just followed the blood trail,’’ he said.

He points to a photo that pops up on the screen.

“That’s me in uniform, 20 pounds lighter,’’ he said. “Alright 30.’’

Danny McDonald can be reached at daniel.mcdonald@globe.com.