West Fork – Mojave River

Just Sayin’

I suppose, if there is any hard and clear boundary to the Mojave Desert that this is where it is. Over time, the Mojave River has cut away the bluff in Summit Valley, east of the Cajon Pass, as the Mojave Desert moves with the rest of the Mojave Block as it separates from the San Bernardino mountain range.

https://digital-desert.com/mojave-river/