Created by Tom Fontana and co-produced by Fontana and Barry Levinson (the same team responsible for Homicide: Life on the Street), the gritty, uncompromising cable drama series Oz was set within the walls of Oswald Maximum Security Penitentiary (later rechristened Oswald State Correctional Facility), known to inmates and guards alike as "Oz". In a similar burst of grotesque whimsy, the action took place in "Emerald City," an experimental "prison within a prison," wherein the inmates were allowed to function as a more or less autonomous community, awarded with mobility and privileges in exchange for submitting to a daily routine and a strict set of rules and guidelines. Emerald City was established at the behest of Warden Leo Glynn (Ernie Hudson) by idealistic unit manager Tim McManus (Terry Kinney), who hoped that by giving the inmates a sense of community and responsibility, he could smooth the road to rehabilitation. Unfortunately, there were some convicts who just couldn't see things from McManus' "New Age" perspective, leading to sundry outbreaks of violence and bloodshed throughout the season's six-year HBO run. Additionally, Glynn and McManus were at the mercy of Governor James Devlin (Zeljko Ivanek), who sailed into office on a tough law-and-order platform, and who was dead set against McManus' alleged coddling of Em City's most dangerous cons. As it happened, Devlin's administration was itself waist-deep in corruption and collusion, making his entire pro-law stance somewhat laughable (except that no one was laughing).

As for the inmates, they had divided themselves along ethnic and personality lines into various tribe-like factions, eternally enmeshed in deadly power struggles. Among these "tribes" were The Brotherhood, The Homeboys, The Muslims, The Italians, The Irish, The Latinos, The Gays, and a nebulous bunch called "The Others," of which the series' narrator, wheelchair-bound con Augustus Hill (Harold Perrineau Jr.) was a member of long standing. The series boasted an enormous cast of characters on both sides of the bars. Those who were seen throughout the series' entire run included the aforementioned Leo Glynn, Tim McManus, James Devlin, and Augustus Hill (who remained a key player even after he was killed at the end of season five!), as well as inmates Miguel Alvarez (Kirk Acevedo), Kareem Said (Eamonn Walker), Zahir Arif (Granville Adams), Vern Schillinger (J.K. Simmons), Tobias Beecher (Lee Tergesen), Bob Rebadow (George Morfogen), and the funky philosopher known as Poet (muMs).

Of the authority figures, those who went the full six-year distance included prison infirmary doctor Gloria Nathan (Lauren Velez) and spiritual leaders Sister Peter Marie Reimondo (Rita Moreno) and Father Ray Mukada (B.D. Wong). Other recurring characters worth noting were volatile inmates Chris Keller (Christopher Meloni) and Simon Abedisi (Adewale Akinnouye-Agbaje), self-proclaimed escape artist Agamenon "The Mole" Busmalis (Tom Mardirosian), pregnant convicted murderer Shirley Bellinger (Kathryn Erbe), pro basketball player-cum-convict Jackson Vayhue (Rick Fox), imprisoned televangelist Jeremiah Cloutier (Luke Perry), sympathetic prison guards Sean Murphy (Robert Clohessy) and Diane Wittlesey (Edie Falco), and not-so-sympathetic turnkeys Claire Howell (Kristin Rohde) and Clayton Hughes (Seth Gilliam) -- the latter a psychopath who ended up attempting to assassinate Governor Devlin. Debuting July 12, 1997, Oz turned out between eight and 16 episodes per year (running times varied from 45 to 70 minutes), until its final first-run installment on February 23, 2003.