Win the game while all trading post spots (either by a native camp, or on a trade route) are occupied by you. Build a trading post (or tambo if you're Inca) on the slot next to them to occupy them.
You can do this on any map, but Alaska is a very small one. It only has two spots to build, each on a native camp. There is no trade route to bother with.
To win easily, use the cheat code 'tuck tuck tuck' a few times to spawn a powerful monster truck that kills anything it drives near.