Port Royale 3

This requires you to take towns by force as you can only peacefully take control of a town if the host nation has at least 5 towns still under their control. If you are playing the Trader campaign or have started a Free Play game in 1550, then the easiest way to achieve this is by attacking the Dutch as they only have 5 towns to begin with.

Refer to "…vici" for more information on taking control of towns.