What type of habitat do squirrel live in?

I live in Northern California and I have one that lives in and around my backyard. It jumps from tree to tree and comes into my front and back yard to tease the neighborhood tom cats. It is quite comical but it lives in suburbia terrain. I see them all over California and have seen them all over Colorado as well. I have seen them in Nevada and Idaho. Give them a tree and some water and I think they can live anywhere they can forge for food.