Mueller Family Vineyards is located in the Napa Valley on 10 acres on Diamond Mountain near Calistoga. The Diamond Mountain District or AVA is located above the valley floor, west of Highway 29 between Calistoga and Spring Mountain, north of St. Helena. Most of Diamond Mountain and its peak are actually in Sonoma County, but the wine-growing reputation of the mountain comes from the Napa Valley side. It encompasses some 5,000 acres, of which less than 500 are planted to vines, making this the smallest AVA in the Napa Valley. The name, “Diamond Mountain” apparently comes from the sparkling mineral crystals and obsidian found in the soil here.