Joshua 19:41

And the coast... — Zorah and Eshtaol, in the tribe of Dan, had been originally assigned to Judah (Joshua 15:33); so also Ekron. But it is not clear whether they are mentioned here as marking the border of Dan and Judah, or actually in the territory of the former. However, Dan is wedged in, as it were, between the powerful tribes of Judah and Ephraim, the unconquered Philistines, and the sea. It is not surprising that their coast “went out from them” (Joshua 19:47) when it was partly unconquered, partly taken from other tribes in the first instance. Conder says it was carved out of the country of Ephraim.