What is the max population that you were able to achieve in a town?

[Raffo]

I'm playing it after many years, but I think I was able to reach something like 11k or 12k. But I wonder if the limit is much higher with good space management.

[Elondrius]

Honestly I never wanted to go that high. Above 6000 you get every benefit you can, so theres's no real practical reason to go much beyond that. You can be safe and pack on top of that 500-1500 residents, if something goes awry, of course.
If you really want to try the limits, your own town is your best bet, 'cause no other merchant can build there and mess up the space. I think the free space in different towns varies as well, but I don't think that means much, maybe one or two buildings. On the other hand looking at a town full of buildings without any grass, tree or a bit of a desert is quite depressing.

[MoS]

Currently trying to populate Caribbean Basin as much as possible... Soon, I will try to post an image that shows just an interim status of my current gameplay, for some viceroy + governor cities having 12 to 17 000 pops without any optimization.

... this is before beginning the real new party, " from stratch ", in a few weeks.

With 60 official + 16 dedicated towns, I think reaching to 1 000 000 inhabitants will be a trivial assignment,

... forcing 1 200 000, will be my challenge.

Edit:

https://steamcommunity.com/sharedfiles/filedetails/?id=2252932675