Cool quiz. I missed St Petersburg.. thought of it but when I tried Moscow and that wasn't on here I didn't think St Petersburg would be bigger even in 1900. Only other one I missed was Vienna but should have got that one, too. Capital of the Austro-Hungarian Empire at the time I think.
We were still mostly rural in the farms, we were too poor to go to the city. Until later on during the Mao's Cult Revolt the farmers started mass migrating to the cities and populating them. Soon many cities developed quickly.