The Rockpile wine grape growing area in northern Sonoma County is one of the smallest AVAs in the country in total acres of grapes planted. There are 160 acres of vineyards sitting between 800 ft and 2,100 ft elevation in rocky, well-drained soil with maybe a foot of topsoil at the surface.
The wines from here are a rare treat with so little vineyards planted. It's mostly zinfandel and cabernet sauvignon, but there are several others. The cab franc and petite sirah from here are also excellent. It's almost entirely red wine grapes.