Think of Prohibition in the United States and images of speakeasies and moonshiners come to mind.

But books and movies about gangsters of the 1920s and 1930s tend to focus on the trade in illicit whiskey and gin in the north and east of the country, ignoring the lively trade in the south.

Dennis Lehane in his 2012 novel, Live By Night, wanted to correct that oversight. "I wanted to do a book about the rum trade," the 51-year-old writer tells The Straits Times on the telephone from the United States.

He is known for novels set in his hometown, Boston, including Mystic River (2001) and Gone, Baby, Gone (1998), both of which were adapted into films. But he also lived in central Florida for some years, he says.

"I thought it would be sexy to do a gangster novel with a Latin influence, set in the 1920s. I had not seen that before," he says.

Live By Night, the film based on Lehane's book and starring Ben Affleck, opens tomorrow.

The character of mobster Joe Coughlin (played by Affleck, who also directs) moves to Florida in his 20s, only to face culture shock.

The same thing happened to Lehane when he moved there, he says.

When he lived in Florida, he came to know the history of places such as Ybor City, a district in Tampa.

Rum-runners, who had links with Cuba and its revolutionaries, had a century ago excavated a maze of tunnels under the streets - a feat that must have taken remarkable persistence and engineering skill, given the area's water-logged soil.

"You never find basements in Florida. You can't build underground - it floods, the earth collapses. And yet, every now and then, they will tear down a building in Ybor City and, to this day, find evidence of one of the tunnels," Lehane says.

In the book and the film, Coughlin and crew use the tunnels to transport and store rum under the noses of the police.

"The tunnels are fascinating. It's like building on top of the Egyptian pyramids," Lehane says.

The caverns form part of the book's rich backdrop.

Lehane sought to create a tapestry that included men and women from every layer of society, from politicians to police to revivalist preachers, personified by Loretta Figgis (Elle Fanning).

"I let my imagination run - I wanted to create a world that was like the movie Casablanca. I wanted it to feel like that, to feel dangerous and sexy and filled with criminals, revolutionaries, trade union activists, working- class people and corrupt judges," he says, referring to the 1942 classic.

The film and book show a world in which gangsters wield enormous political power because bootlegging has made them wealthy.

Lehane says "you can't mistake the correlation" he is drawing between the banning of booze almost 100 years ago and the war on drugs in the US today.

"When you try to legislate morality, particularly when you try to legislate non-violent vice, bad things happen."

•Live By Night opens in Singapore tomorrow.