Build a town with 100 stone houses.
Another self-explanatory achievement, but remember that stone houses take a lot of stone to build, and a too rapid rate of building can cause overpopulation and isolation of people.
If you're running out of stone, build some trading posts. As long as you have other resources to trade, you'll have an easy supply of stone.
Make sure that you don't build the houses too fast without enough food supplies - you'll quickly find your food will run out otherwise.