Caveat: I haven't lived in Dallas for a long time.

But there was a definite cut-off past which it wasn't "Dallas" to us, anymore. Anything west of Arlington was definitely Fort Worth.

But I wonder if people from Fort Worth considered Arlington to be part of their city, and anything east of Grand Prairie was their cut-off line.

I suspect not. There's a large natural physical barrier stretching from Kennedale to Mosier Valley.

Village Creek is the cultural divide betweenvthe cities on both sides.

It shows how long it's been since I lived there, and how little I went to Fort Worth - none of those names ring any bell to me at all.