Joshua - Chapter 18
Survey of Israeli Geography 101
The Tribes of Judah and the sons of Joseph were settled in their territory, as were the Tribes with land in Trans-Jordan. Since Levi did not have a territory, this left seven Tribes waiting to receive their portions. Joshua had each of these Tribes select three members who would survey the land and describe its features. The land would then be divided into seven portions and distributed by lottery.
The first portion drawn went to the Tribe of Benjamin and fell in between the portions of Judah and Ephraim. The Navi describes the territory in some detail, then ends with a listing of cities in the territory, one of which was Jerusalem.
But wait! Didn't we say, back in chapter 15, that Jerusalem was in Judah's territory? Actually, the city of Jerusalem was shared by the Tribes of Judah and Benjamin. (Think Kansas City, lehavdil.) There is some discussion as to the exact location of the altar - see the commentary of the Radak on 18:28, citing the Talmud in Zevachim 53b and Deut. 33:12.