Randa Abdelfattah and Ramteen Arablui

Alphonse Al Capone, his main rival in Chicago, also known as Scarface.

There were other kingpins who were just as large, but Al Capone, man, he was like the poster child.

Capone had moved to Chicago at the start of Prohibition in 1920.

Suddenly, they take an industry that is big and lucrative, the alcohol industry in the U.S., and they make it illegal.

And there's immediately a booming market for illegal alcohol.

This is Joe Thorndyke, historian for Tax Analysts, a nonprofit provider of tax information.

And in places like Chicago, this was very evident.

Chicago was an ideal place to build a bootlegging empire.

A big city, centrally located, with notoriously corrupt law enforcement.

But it was also true in almost every big city.

Prohibition didn't start organized crime.

The early 1900s, there was this culture of corruption.

So they already had the infrastructure.

This is Paul Camacho.

He's a retired special agent for the IRS Criminal Investigation Division.

And he's on the board of directors at the Mob Museum in Las Vegas.

But Prohibition came in and it was like the goose that laid the golden egg.

These people get really rich.

They could buy the protection of police officers, of prosecutors, of judges.

They could also threaten all of those same people with violence.