The introduction of birth and death records alongside detailed census information means we now have an accurate idea of population size for countries, states and cities across the globe.
However, when looking back at the historical population of different regions, it can be far more difficult to establish the precise number of residents.
The global population reached one billion in 1804, rocketing from there to 8.2 billion by 2024, although it is far less clear exactly which city reached one million first.
By collaborating the findings of various historical researchers and social scientists, the first ‘million person city’ can be narrowed down to three areas: Rome, Baghdad or Chang’an.
One of the most renowned estimations of the global population was published by American historian and author Tertius Chandler in 1987. His work included estimates of the populations of some of the world’s major cities since ancient times.
His work was subsequently followed by similar investigations conducted by Professor George Modelski and historian Ian Morris in 2003 and 2010 respectively.
According to Chandler’s original estimates, the city of Baghdad, the capital of Iraq, was the first city in the world to reach the milestone of one million residents.
However, this historical world view is disputed by both Modelski and Morris who instead suggest Rome, the capital of Italy, reached one million residents far earlier.
To further complicate the issue, all three suggest slightly different time periods for when China’s ‘million man city’ Chang’an actually achieved a population of this size, despite the region being historically recognised for its remarkably high population.
According to Chandler’s estimates, Baghdad was the first city to host one million residents and reached a record-breaking population size in 925AD.
Chandler does record the Chang’an population as steadily rising from 400,000 to 800,000 between 637AD and 750AD, however, Baghdad reaches the million mark first.
Modelski estimates Baghdad reached a population of roughly 1.2 million in the year 1000 AD, which broadly aligns with Chandler’s theory. However, he estimates that Rome’s population reached one million first in 100 AD.
Morris strays even further from the other works by suggesting Rome reached one million residents by 1 AD, centuries before Baghdad. Additionally, he estimates Chang’an did achieve a population of one million around 800 AD, also ahead of Baghdad.
While historians cannot agree on a lone city which broke the record, the repeated acknowledgment of Rome, Baghdad and Chang’an as cities with consistently high and growing populations suggests that one of these three reached the global milestone first.
