This question can encompass a lot. For starters, they are the only cities left after the great war. One good; one evil. The gods decided to spare these cities and leave them as the last bastions of civilization and...you know what? I'm not a storyteller. School yourself nooby
(j/k click on the link below and you will find out all about this wonderful place called Norrath)
Tome of Destiny They are also the starting cities.
Enjoy the Tome!
Edit: Bah, Tutan too fast!
Edited, Mon Aug 1 15:05:45 2005 by Mearyk