This was the heyday of the pre-Prohibition gangs, roving bands of violent toughs who terrorized ethnic neighborhoods and often fought pitched battles with police. In 1903, the Battle of Rivington Street pitted a Jewish gang, the Eastmans, against the Italian Five Pointers. When the cops showed up, the two underworld armies joined forces and blasted away, resulting in three deaths and scores of injuries. The public was clamoring for action against the gangs.
Problem was the gangs worked for Tammany. The Democratic machine used them as shtarkers (sluggers), enforcing discipline at the polls and intimidating the opposition. Gang leaders like Monk Eastman were even employed as informal “sheriffs,” keeping their turf under Tammany control.
Sullivan knew the gangs would flout the law, but appearances were more important than results. Young toughs took to sewing the pockets of their coats shut, so that cops couldn’t plant firearms on them, and many gangsters stashed their weapons inside their girlfriends’ “bird cages” — wire-mesh fashion contraptions around which women would wind their hair.
Ordinary citizens, on the other hand, were disarmed, which solved another problem: Gangsters had been bitterly complaining to Tammany that their victims sometimes shot back at them.
FWIW, some Chicago politicians have close ties with gangs. On the national level... We wonders, aye, we wonders.