I grew up with three styles:
New England - milk or cream
Manhattan - tomato based
Rhode Island - Chris's
I still have my great grandmother's recipe for all of them in the recipe book she gifted to my grandmother for Christmas in 1938 after she, my grandfather(her son) and their children and my grandmother's sister had moved back to Shelter Island, NY.
I have eaten so much clam chowder IF I ever eat anymore it will be too soon.
Sorry for being snarky. I can post the recipes if I haven't already …...my mom used to win awards with the Manhattan and that is what we always had for the night before Thanksgiving instead of pizza