At one time they say the Gulf of California extended all the way up to the area of Indio. And in more recent times that area down through there was actually a very large freshwater lake vastly bigger than the Salton Sea. If you know where to look on the hillsides you can still find ancient rock fish traps constructed by the Indians on old shorelines. In fact you can still identify terraces where the water cut into those hillsides.
If it were not for silt coming down with the Colorado River the Gulf would probably still range all the way up to Indio.
The Colorado River has pretty much filled in the northern portion of the Gulf of California (or Sea of Cortez which I think is a more romantic sounding name for it).