I recently read in The Economist that in 1900 London was the largest city in the world, "with 6.5 million inhabitants and streets thronged with omnibuses, hackney cabs and horse-drwan carriages."
However, I have also always heard that Tokyo has been the largest city in the world ever since about the ~1860s. (It is still the largest urban centre today, is it not?)
So, historically, what have been the largest urban agglomerations of humanity? Was the booming London or the bustling Tokyo biggest in 1900? Or does it really not matter? :-)
Thank you for your thoughts on this.
It's true that Tokyo (Edo) Was the largest urban center in the world in the 1860s (and indeed, had been the largest urban center since the early 17th century and the unification of Japan), but after the Meiji Restoration in the late 1860s, the population declined enormously due in large part to the end of the Sankin Kotai (A Tokugawa policy designed to control the Daimyo by forcing them to spend half their time in Edo, closer to the shogun). The new government did not maintain the policy, and as a result Daimyo and their households departed the city, directly reducing the population as well as depriving the city of some of its largest consumers. Combined with the effects of a civil war, it would take 20 years for Edo's (Now called Tokyo) population to recover.
Here's a nice chart which compares Tokyo's population to London's:
Source (and a good read if you have Jstor): http://www.jstor.org/stable/40113289
So, the first part of your question we can answer. I dug around really quick and found the following:
"London's population in 1809: 1,000,000+; in 1841: 1.9 million; in 1850: 2,350,000; in 1861: 3.8 million; in 1890: 4,000,000+; in 1901: 4.14 million. Greater London had a population of 6,000,000+ in 1900."^^1
So, at 1900 London had a population of 6,000,000.
Tokyo at that point had a population of 1,497,000.^^2 So without a doubt, London was the largest city at the time. It wasn't until the late 20th century that Tokyo became the largest city in the world.
The overall question on the biggest agglomerations is more of a survey question and is against the rules of the subreddit!
Sources:
^^1 http://www2.uncp.edu/home/rwb/london_19c.html
^^2 http://teacherweb.ftl.pinecrest.edu/snyderd/MWH/readings/Urban/City%20Pop%20-%20History.pdf