A post-nuclear megalopolis covering much of what is now the Eastern United States and some of Canada, the city's exact geography depends on the writer and artist working the story.

However, when artist Carlos Ezquerra drew his first story for the series, a skyscraper in the background of one panel looked so futuristic that editor Pat Mills instructed him to draw a full-page poster of the city.

Art director Doug Church suggested that the city should extend along the entire Eastern Seaboard, and be called Mega-City One, and his idea was adopted.

[4] The back of prog 3 included an Ezquerra "Futuregraph" poster of Mega-City One (a page from an unused Dredd story), which said the city stretched from Montreal to Georgia and had 150 million citizens; it was part of the "United States of the West" (USW).

Mega-City One evolved out of a growing conurbation stretching from Boston to Washington DC, which took form in the 21st century to cope with the escalating population crisis in the United States and – as a solution chosen to deal with the high crime rate – led to the introduction of the Judge system.

[12] Maps of the city[13] show that in the early 22nd century, it stretched roughly from southern Maine down through Florida and to the north-east has absorbed the Quebec City-Windsor Corridor in Canada.

The Hab Zone was mostly ignored by the city and Sector 301 became disparagingly nicknamed "The Pit" due to its high crime rate, until Chief Judge Volt had it cleaned up in 2118.

[16] However over the following few years the city began to grow again due to immigration, taking in of refugees and the gradual return of millions of citizens who sat out the plague overseas and off world.

However the destruction of the Academy of Law during Chaos Day has disrupted the supply of cadets, and it is all the remaining judges can do to cope with the expanding population as it will be years before replacement of losses is reliable again.

By this point then Chief Judge Hershey believed the city could once again safely absorb such a vast increase in numbers, as many undamaged blocks remained available to be re-inhabited.

[24] In 2113 a referendum was held in which the people were allowed to decide whether to restore democratic government, but by this time the memory of democracy had become so distant that the majority of citizens did not bother to vote, and most of those who did opted to retain the status quo.

[25] In the early years of Judge Dredd, Mega-City One had not been established as a dictatorship – "The Purple People Breeder" (2000 AD Sci-Fi Special 1978) mentioned "presidential candidate Howard Surb", while "Ryan's Revenge" (Dan Dare Annual 1979) had the Mayor giving orders to Justice Department.

The Luna-One story arc briefly mentioned the governing body "the Grand Council of Judges" and "the Triumvirate", part of a unified state called the United Cities of North America,[26] but this was dropped by prog 61.

[34] When a street judge retires from service at the end of his career, he may choose to take the "Long Walk", leaving Mega-City One for exile outside its borders.

While there was heavy protest in Congress over the idea of abandoning due process, the electorate was in favour and President Gurney (who supported Fargo's plan) was re-elected with a massive majority.

[35] The original uniforms heavily resembled those of normal American police officers, albeit with helmets and heavy body armour, and rode Lawranger motorcycles.

98% are unemployed (due to advances in robotics) and range from lazy and sloth-like to highly rebellious violent criminals, bent on destroying and killing as much as they can for whatever reason they can think of at that time, if any.

For example, in his Christmas message, Chief Judge Francisco asked citizens if a large number that were on welfare could commit suicide in order to help balance the budget for the following year.

[38] The citizens occupy their time with many strange and outright bizarre hobbies, such as simping (recreational stupidity), bat gliding, sky surfing and peeping (spying on people at home and in public), which is illegal when done for voyeuristic purposes, but legal when done under the authority of a Judge.

Most are poorly educated and many can barely read or write, some sectors are said to be entirely illiterate,[39] but Judges aren't that concerned, as it makes it easier for them to control and they can weed out the more intelligent simply when major crimes occur.

Most of the city's biggest advancements in areas such as food, new materials, technology (unrelated to weaponry), medicine and architecture and construction design (including the Halls of Justice) came from ordinary citizens.

All the major businesses and entertainment (apart from Justice Department propaganda channels) figures are citizens as are a lot of the city's diplomats, but they always report to a Judge before making any decisions.

In extreme cases, even the death penalty may be imposed, although relatively sparingly compared with the present day, and reserved for mass murder or the endangerment of the security of the city, but sometimes it is used simply to make an example or to intimidate the citizens.

A violation that would earn a citizen a few months in an Iso-Cube would get a Judge a twenty-year sentence, served as hard labor on Saturn's moon, Titan, after surgical modification to enable the convict to survive outside without needing an expensive space suit.

Torture is normally illegal, but in extreme circumstances and with orders from the Chief Judge they employ it (both physical and psychological), for example when time is of the essence due to the city being in severe danger (or the Justice Department's authority is).

[45] The Judges covered this up, "arresting" them by faking heart attacks, strokes or whatever was realistic or convenient at that time and then told their next of kin they had died, with this they could do whatever they wanted to them.

During crises inside the city, regular Judges or Citi-Def are almost always shown doing the fighting instead and the military is usually mentioned in outer space – "Day of Chaos" eventually explained that they're unlicensed to act against the civilian population.

In very rare, desperate and often last stand scenarios the Justice Departments auxiliaries are issued weapons and fight alongside Judges, such as in the latter stages of both the Apocalypse War and Judgement Day.

[56] Boredom has fostered many problems in the city, with citizens spending their leisure time rioting over jobs, experimenting on their neighbors, and running amok in the streets.

According to Judge Dredd (Karl Urban), the boundaries of Mega-City One reach "from Boston to Washington D.C." (similar to the real-life concept of the Northeast megalopolis) and contains a population of 800 million.