Elkosh appears in the Bible only once, in the first verse of the book of Nahum. There the prophet is identified as a native of this place, before announcing the fall of Nineveh.
Apart from this mention, the biblical text says nothing more about Elkosh. There is no account of any event there, nor any other passage that helps locate it with certainty.
Evangelical scholars acknowledge that attempts to identify the place have not succeeded. At least three different regions have been proposed: Galilee, southern Judah, and northern Mesopotamia, near Nineveh.
What this brief mention truly teaches is that God raises up his messengers even from places with no other record in history. A prophet from an almost unknown town received the vision that announced the fall of the most feared empire of his time.