The Springfield Mafia is an Italian-American Mafia crime syndicate based in Springfield. The premier family among the Springfield Mafia is the D'Amico Crime Family.
Gambling is possibly the gang's most profitable venture.
The gang has strong control over illegal fireworks sales and rats milk production.
The gang helped out Marge Simpson's pretzel business by putting her competitors out of business.
The mafia is also responsible for tobacco, drug, and alcohol trafficking. When Springfield reenacts Prohibition, he pays off police officers to smuggle the booze into the town.
The gang offers protection to Krusty Burger from competitor restaurants such as McDonalds and Burger King.
The mafia also built a wheelchair navigation ramp system for Springfield Elementary School, which ended up collapsing due to being made out of breadsticks before it could see official use (It was originally developed to help Bart get around the school when he was confined to a wheelchair, but that fell through after he made an unexpectedly quick recovery), which also forced Springfield Elementary to close permanently.
The Mafia often punishes people for things that are either an insult to them or if they don't pay back their debts. For instance, when Homer ended up borrowing money from Fat Tony and losing it in a football game, Fat Tony "hammered down" a payment plan by having Louie hammer Homer's hand (using two hammers if he mentioned Professor Pigskin).