Wikipedia - Southern Illinois [link to en.wikipedia.org]
Southern Illinois (most of which is known as "Little Egypt" or "Egypt") is the southern third of the state of Illinois. With the area code 618, the southern part of Illinois is geographically, culturally, and economically distinct from the rest of the state. The region is surrounded on three out of four sides by the most voluminous rivers in the United States, the Wabash and Ohio rivers to the east and south, and the Mississippi River and its connecting Missouri River to the west.

One thing I find really interesting is that Wikipedia made it a point to mention the area code. It's actually the very first thing it says! I find this interesting because of the number itself , 618.