The triple life of G-Rock: upscale house painter, lifelong Crip, FBI informant.

On L.A.’s Homeboy Industries, which offers former felons—including at least one disgraced CEO—the chance to work.

Rogue cops in the LAPD Rampart division’s anti-gang CRASH unit (Community Resources Against Street Hoodlums) were involved in everything from drug smuggling and bank robberies to, allegedly, the murder of Christopher “Notorious BIG” Wallace.

Chains, knives, fists, and, of course, those crude and unreliable homemade affairs called zip guns were the staples in the more vicious gang wars in the 1940s and 1950s. Today there is scarcely a gang in the Bronx that cannot muster a factory-made piece for every member—at the very least, a .22-caliber pistol, but quite often heavier stuff: .32s, .38s, and .45s, shotguns, rifles, and—I have seen them myself—even machine guns, grenades, and gelignite, an explosive. One gang, the Royal Javelins, has acquired some walkie-talkie radios.

Nicky Louie and the Ghost Shadows.

The narcocorrido-immortalized Pacific coast traditionalists, the kidnap-crazed Gulf coast Zetas, and massacres that no longer seem tied to a discernible purpose; inside the ruins of the Mexican-American border.