In Chicago, the brands are Pioneer and Cargill - the Cargill brand is listed as cane sugar, not pure cane sugar so who knows if it's 100%. Companies play too many games these days, you have to be paranoid.
If you had asked me, 2 years ago, I would not have cared but the more I learn about products, the pickier I become. I bake a lot and I'm used to Domino Sugar(I think they make C&H), but I like their brand because it's extra fine and not the harsh crystals that's normally available.
You guys in California are so fortunate - great weather, great products. I was there a couple months ago and was so excited for Diamond Crystal Kosher salt. In the midwest, the common brand is Morton's - but you can look hard to find DC. I actually went to a specialty butcher for mine.