In the period between 1880 and 1920, five major gangs controlled the underbelly of Manhattan. These gangs were the Whyos, the Hudson Dusters, the Five Pointers, the Eastman Gang, and the Gophers. Other gangs existed in Lower Manhattan – the Hartley Mob of Houston and Broadway, the Molasses Gang and the Mackerelville Crowd to name a few - but they were rather minor in comparison to the numbers and operations of the substantial five. There were a few gangs such as the Red Peppers and the Rags Riley’s Pansies scattered towards the northern spread of the island, but at the time that land was low in commerce and considered relatively desolate and unfruitful.

The Big Five

The Whyos
The Name Came from the gang’s cry, which, to an uneducated bystander, sounded like a bird or owl calling, “Why-oh!”
The Territory All over Manhattan
The Headquarters Shifted many times through the years: “Dry Dollar” Sullivan’s Chrystie Street saloon, a churchyard at Park and Mott Streets and even a Bowery dive called The Morgue (named such because the owner proclaimed his refreshments were useful as drinks or embalming liquid).
The Leader The Whyos had several, but the captains with the records for longevity were Danny Lyons (arrested for the murder of his girlfriend’s lover) and Danny Driscoll (hanged at Tombs for the murder of a saloonkeeper).
The Times 1874 to 1890’s, when the gang dissolved due to most of the members dying or going to prison.
The Members were entirely Irish, but unlike the Irish gangs of the past, victimized anyone - not just Englishmen. Driscoll and Lyons eventually decreed that in order to be a real Whyo, the person must have killed at least once. They were so powerful that most of the other gangs at the time had to ask their permission to operate.
The Crimes Pickpockets, sneak thieves, dive owners, and brothel and panel-house keepers. The Whyos also offered services:

 

Punching $2
Both eyes blacked $4
Nose and jaw broke $10
Jacked out $15
Ear chawed off $15
Leg or arm broke $19
Shot in the leg $19
Stab $25
Doing the big job $100 and up

 

The Gophers
The Name Consequent of their routine of holing up in basements and cellars. The name is usually pronounced “Goofers”, although not derogatorily.
The Territory Controlled the middle West Side, from Fourteenth to Forty-Second Streets and from Seventh to Eleventh Avenues; they were the kings of Hell's Kitchen.
The Headquarters A saloon on Battle Row (Thirty-Ninth Street between Tenth and Eleventh Avenues) run by their leader.
The Leader In its heyday: Mallet Murphy, whose moniker was bestowed due to his usage of a mallet as a weapon. Chiefs: Newburg Gallagher, Marty Brennan, Stumpy Malarkey, Goo Goo Knox, One Lung Curran, and Happy Jack Mulraney, who suffered from a facial rictus and once killed a barkeep for laughing at him.
The Times 1890’s to the 1920’s
The Members 500+; there were also the free companies under Gophers: the Gorillas, the Rhodes Gang, the Parlor Mob and the Battle Row Ladies’ Social and Athletic Club (also called the Lady Gophers and led by Battle Annie)
The Crimes Brawlers, muggers, thieves, and freight car robberies (eventually the railroad established a police force just to deal with the Gophers, which eventually led to their demise). In 1908, under Big Jack Zelig, they also came to openly advertise services:

 

Slash on cheek $1 to $10
Shot in leg $1 to $25
Shot in arm $5 to $25
Bomb $5 to $20
Murder $10 to $100

 

The Hudson Dusters
The Name came from the territory that stretched down the western side of Lower Manhattan, starting at the Hudson River
The Territory As above, the Hudson side of Lower Manhattan and east to Broadway; north to Fourteenth and south to the western tip of the Battery. They took over what used to belong to the Potashes and Boodles after those gangs disbanded.
The Headquarters A single place was not designated as “headquarters” per se, as they kept their base of operations transient, but it’s said that they had places on Bethune and Hudson Streets.
The Leader Kid Yorke and Circular Jack, along with Goo Goo Knox (who left the Gophers after a conflict, although the Gophers and the Dusters later became allies), founded the Dusters, but I haven’t found mention of a captain yet.
The Times 1890’s to 1916, when the Marginals, who had been vying for Duster territory, finally took control of the West Side docks.
The Members were lively show-offs, rather disinterested in mayhem but loving publicity just the same. Most of them were addicted to cocaine.
The Crimes “The Dusters boasted a legendary thief called Ding Dong, who had organized a corps of children who would assist him on his rounds by climbing onto express wagons and throwing parcels down into his waiting arms, after which they would disappear.” –Low Life, Luc Sante

 

 

The Five Pointers
The Name was based more on sentiment than location, since the actual Five Points had been destroyed by fire nearly 30 years prior. The intended emotions evoked were apprehension and dread, no doubt, since the gangs of that area were the most ruthless and vicious in the city’s history.
The Territory was confined to a relatively small area from Fourteenth Street down to City Hall, between Broadway and Bowery. On their turf was a so-called “underworld one-stop store” which sold things such as pistols, brass knuckles, stilettos, billy clubs (the house-manufactured brand had a lead slug in the end), and blackjacks (six-inch leather bags filled with shot, ending in a rope handle).
The Headquarters New Brighton Dance Hall on Great Jones Street
The Leader Paul Vaccarelli, a.k.a. Paul Kelly, with principle lieutenants Biff Ellison (successful racketeer who ran the short-lived Paresis Hall on Cooper Square), Eat-‘Em-Up Jack McManus (famed mayhem artist and sheriff of both the New Brighton and McGurk’s Suicide Halls), Kid Dropper (con artist extraordinaire), and Johnny Spanish (hold-up artist).
The Times Early 1890’s to the 1920’s, although they are the predecessors to the Gambino family, which is still active today.
The Members eventually boasted 1,500 subordinates, such as Al Capone, Terrible Johnny Torrio, and Lucky Luciano. They were dandies - clean-shaven, manicured and well-dressed. Paul Kelly and Biff Ellison were immortalized in Caleb Carr's novel, The Alienist 
The Crimes were unlimited, as evidenced by the Five Pointers’ lieutenants. They seemed to be involved with all manner of crime conceivable.

 

 

The Eastmans
The Name Named after the founder Monk Eastman.
The Territory The Eastmans ran the business from the Bowery and to Monroe street, which headed up to the East River. They also had smaller conglomerates: The Cherry Street Gang (a rejuvenated form of river pirate) and the Yakey Yakes, who roosted under the Brooklyn Bridge. Their territory included the East Side brothel district and more than a fair share of Bowery dives, which just happened to be on the east side of the street.
The Headquarters were at a shady Chrystie Street saloon, from which police once raided two wagons filled with weapons.
The Leader was an animal lover whose first job was in a pet shop. Restless, he took a job as sheriff at the New Irving Dance Hall, and became proficient with all sorts of defense weaponry and knockout drops. Whereas most of the gangsters of the time were well-kept and fashionable, Eastman was crude in appearance. While his reputation for ruthlessness soared (he once cracked an innocent bystander's head open with his club because "I had 49 nicks in me stick, an' I wanted to make it an even 50"), so did his love for animals. He eventually opened a pet shop of his own, but the business went bad because he refused to sell the animals. He was one of the most ruthless and violent gangsters of all time, continually rivaling Paul Kelly.  
The Times Mid-1890's to 1904, when Eastman was arrested by a Pinkerton detective. The gang survived a few years afterward, but desperately needed Eastman's leadership. 
The Members were, like the Five Pointers, dandies. At one point, members were required to turn in typewritten reports on contract jobs. They ran a large amount of business under the cover of balls, organized outings, laundered cash and trafficking through outfits such as the Jolly 48, the Soup Greens, the East Side Dramatic and Pleasure Club, baseball clubs and female auxiliaries.
The Crimes were also unlimited.

 

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