Detective Joe Teague
A former US Marine Corps Master Gunnery Sergeant and Guadalcanal Campaign veteran caught in the conflict between Parker and Cohen.
- Always Save the Girl: His driving motivation is to protect Jasmine. He will do anything and everything to save her, no matter the consequences.
- Awesomeness by Analysis: His detective skills can't be denied.
- Berserk Button: Threatening or endangering Jasmine.
- Dirty Business: He murdered Hecky Nash to protect Jasmine from Siegel.
- My God, What Have I Done?: Nearly killed Jasmine while having a Flashback Nightmare years earlier. This brought an end to their marriage.
- The Stoic: Though a bit gruff, Teague is regularly a pretty taciturn fellow.
- Not So Stoic: He gets pretty emotional when it concerns Jasmine. Understandable, since he loves her and she's often in danger.
- Take a Third Option: Siegel beats him down and gives him a choice between giving up Jasmine or dying with her. Teague proceeds to follow Ned Stax to his meeting at one of Siegel's houses and shoots Siegel over a dozen times from a distance with his rifle.
A lawyer and fixer for Cohen, who also fought alongside Teague in the war.
- Conflicting Loyalty: Works closely with the gangsters, but is still friends with his war buddy, Joe Teague.
- The Evil Genius: To Bugsy Siegel's criminal empire.
- Unwitting Pawn: His decision to stay by Teague's side after Siegel deals him a No-Holds-Barred Beatdown and Sadistic Choice turns out badly, as Teague follows Ned in his taxi, leading him right to the meeting at Siegel's girlfriend's house. Where Teague assassinates Siegel.
- What the Hell, Hero?: Delivers a few of them to Joe. Most notably, when Joe kills Bugsy Siegel to protect Jasmine, only for Ned to point out that now he's created a power vacuum between Mickey Cohen and Jack Dragna that may lead to an eventual mob war.
Capt. William H. Parker
A captain in the LAPD bent on taking down the mob.
- Cowboy Cop: This is how he is portrayed by Chief Horral, but is in fact more law abiding than most of his colleagues. Interestingly, William Parker was from Deadwood, South Dakota.
- Hero with Bad Publicity: Is criticized and forced to accept the blame for the recent controversies between the LAPD and Bugsy Siegel, despite the fact that he is one of the few honest men working toward justice.
- Honor Before Reason: Though he tries hard to even them out.
- Incorruptible Pure Pureness: A trait he strives to embody.
- In-Series Nickname: Bill The Boy Scout.
- Jumped at the Call: Witnesses young Mickey Cohen's arrest and learns of police corruption one day. He reacts by joining the LAPD and rising in the ranks without compromising his principles.
A beautiful woman working as a photographer at Cohen's nightclub.
- Guile Hero: Is quite skilled at outgambitting the various gangsters she's surrounded by, namely Mickey Cohen.
- Mundane Made Awesome: Replaces a grenade pin with her hairpin to divert an explosion.
Det. Hal Morrison
The detective at the head of the LAPD's new mob squad.
A mobster working closely with Cohen and Siegel.
- Cold-Blooded Torture: Goes Batter Up! on Teague.
- Cultured Badass: Is a talented violinist and a fan of classical comedy.
- Deadpan Snarker: Comes with being played by Robert Knepper.Here's your cheese, lady!
- The Dragon: To Bugsy Siegel.
- Guttural Growler: This is a Robert Knepper character.
- Hidden Depths: Shows genuine remorse when Siegel, his childhood friend, is shot to death in front of him.
- Hypercompetent Sidekick: Rothman is far more charismatic and dangerous than Siegel. He seems to prefer being the Number Two; he's a lot quieter and less nefarious when he's around Bugsy and the other gangsters.
- Made of Iron: Has his head repeatedly bashed against a radiator by Teague, and he walks away smiling like it didn't happen.
- Red Oni, Blue Oni: The blue to Bugsy's red.
The most dangerous mobster in Los Angeles.
- Batter Up!: As a ten-year old petty thief.
- Dragon Ascendant: He's eventually going to control all crime in Los Angeles.
- Dumb Muscle: Though, not as dumb as everyone thinks.
- Hair-Trigger Temper: It's easy to see why he and Siegel get along so well.
- Man of Wealth and Taste: Fancies himself one.
- Psychopathic Manchild: Shows some signs, mostly in that he comes off like a punk kid trying to be a James Cagney character.
- Small Name, Big Ego: He seems to think he's The Dragon to Siegel. The other criminals merely indulge (and, in some cases, guide) the wise guy image he has of himself.
- Troubling Unchildlike Behavior: Attacks a woman with a baseball bat in an attempted robbery around the age of ten.
Mayor Fletcher Bowron
Benjamin "Bugsy" Siegel
One of the most infamous mobsters in Los Angeles.
- Ambition Is Evil: The scene in which Siegel tries to sell Lansky's associates on the idea of Las Vegas also sees him nonchalantly dropping a bound and hooded man into the first building's foundation and having him shot to death.
- Asshole Victim: Considering that this is Bugsy Siegel, not surprising how he suffered a full face of lead poisoning.
- Bullying a Dragon: Joe Teague did not accept his final offer.
- Diabolical Mastermind: Subverted, the East-Coast mob has no patience for the diabolical schemes he has planned, nor his reckless behavior.
- Disc-One Final Boss: The show starts right around the time he is killed, paving the way for Mickey Cohen, Meyer Lansky, and Sid Rothman.
- Embarrassing Nickname: Doesn't like being called Bugsy, apparently.
- Eye Scream: It flies out onto his rug when he is shot.
- From Nobody to Nightmare: He himself lampshades his and Meyer Lansky's rise from poor street hoods to powerful crime lords.
- No-Holds-Barred Beatdown: Dishes them out regularly to people who piss him off enough.
- No Kill Like Overkill: Riddled with bullets by Joe's carbine.
- Rule of Cool: Something he tries to live by. In the first scene of the series, after he, Lansky, and Rothman have slaughtered a group of bootleggers and robbed their shipment, Siegel lights a stick of dynamite with his cigarette and uses it to blow up a car for no reason besides making a bang.
- The Sociopath: He's even worse than the noted sociopath, Sid Rothman, who usually has to calm Siegel down and keep him from cutting people's heads off.
- Stupid Evil: Gets angry and murders a key witness to prove a point to his infinitely more cautious allies. This in turn sets off the disastrous blackmailing plot the first six episodes are centered around.
- Undying Loyalty: Has an entire monologue in which he explains the level of loyalty between himself and Sid Rothman, having grown up together.
- Visionary Villain: This is the guy who laid the groundwork for Las Vegas.
- Walking Spoiler: If the nature of his death isn't already a Foregone Conclusion.
Chief Clemence B. Horrall
The chief of the LAPD.
A lieutenant in the LAPD.
Morrison's Mob Squad
Det. Mike Hendry
A member of Morrison's mob squad that butts heads with Joe.
Det. Tug Purcell
A member of Morrison's mob squad.
- Disability Superpower: Despite losing his glasses and being virtually blind without them, he's able to kill one man and wound another during a shootout. After he's been shot.
Det. Jack "Fat" Bray
An older member of Morrison's mob squad.
Det. Pat Dolan
A member of Morrison's mob squad and Mike's partner.
Det. Nick Bledsoe
A member of Morrison's mob squad and Tug's partner.
Det. Eddy Sanderson
A member of Morrison's mob squad and a friend of Joe's.
Rothman's right hand man.
An Italian mafia boss who frequently tries to invade Bugsy Siegel and Mickey Cohen's turf and take over their rackets.
A brilliant and enterprising East-Coast gangster who is forced to bear bad news to his old friend, Bugsy Siegel.
- Badass Bookworm: Though he is more of an intellectual, the first scene shows him rocking a tommy gun the same as Siegel and Rothman.
- Diabolical Mastermind: He is what Bugsy aspires to be.
- Kosher Nostra: A prominent figure.
- Noble Demon: Maybe not "noble," but Lansky's more composed and diplomatic than any other character, even Ned Stax. He comes off like a pretty nice guy in comparison to Bugsy and Sid.
A standup comedian and childhood friend of Mickey Cohen. Fed up with being looked down upon by the Los Angeles gangsters, he attempts to blackmail Cohen's boss, Bugsy Siegel and escape with his girlfriend to a better life.
- Dead Star Walking: Listing Simon Pegg as a guest star was a big hint.
- Foregone Conclusion: His increasingly desperate "it's my time now" dialogue makes it pretty clear that he's not going to survive, as well.
- Horrible Judge of Character: Hires Joe Teague to be his bodyguard, apparently unaware of the detective's connection to his girlfriend, Jasmine.
- Jerk with a Heart of Gold: He put not only his own life but his girlfriend's on the line to get one over on some powerful gangsters. He also did it so the two of them could have a better life together.
- Old Friend: Has been "friends" with Mickey Cohen since they were little kids.
- Rant-Inducing Slight: Don't get him started on gangsters.
- The Resenter: Towards Mickey Cohen and the other gangsters.
An unstable criminal involved in Hecky Nash's plot to blackmail the mob.
- Butt-Monkey: In the few scenes he has, things never go his way.
- Crazy-Prepared: Emphasis on the crazy.
- Good Scars, Evil Scars: The scars on his lip make him appear quite menacing.
- Wild Card: The mob ambushes him. He reveals a hand grenade, and yanks out the pin. In the middle of a crowded train station.