Although geographically related by their eastern location, there are significant differences between these two places. The Central Valley is California's most productive agricultural area thanks to its abundant sunshine and access to water. The Sierra Foothills frame the northeast end of this central expanse. Due east of Napa, the Capay Valley and Dunnigan Hills (two AVAs rarely seen on US wine labels) lie between the North Coast and the city of Sacramento; to its northeast lie the Sierra Foothills. There are many old vineyards here, as the area was a hotbed of activity during California’s gold rush when plantings first went in. Its remote, mountainous terrain has kept phylloxera at bay. The University of California at Davis is located just west of Sacramento and is the top oenology school in the country. South of Sacramento, Lodi is responsible for approximately 20% of the state’s grape production. It's also a major source for registered sites by the Historic Vineyard Society and has recently received seven official sub-AVAs. Clarksburg sits on the western border of Lodi and at the southern edge of Sacramento. The vineyard area of Clarksburg and the western Lodi subregions enjoy the coastal influence that moves inland across Suisun Bay and up the Sacramento River. This area is home to everything from Chenin Blanc to Mourvèdre. Clarksburg Just east of the San Francisco Bay area and among the waterways of the Sacramento Delta lies Clarksburg AVA, established in 1985. This unique AVA spans three counties: Yolo, Sacramento and Solano. The terrain spans 26,000 hectares, is primarily flat and has rich, fertile soils of clay, silt and alluvial material. The highly fertile soils have poor drainage, and the region is better suited to large production. The waterways here pull in ocean breezes, creating a cool maritime climate, perfect for the main grape grown: Chenin Blanc. Close to 90% of the Clarksburg fruit is sold outside the county, primarily to neighbouring Napa for inclusion in their wines (to use Napa Valley on the label, up to 25% of the grapes can come from somewhere else). Lodi Lodi is a town in the Central Valley of California that also gives its name to the AVA. Some 145 kilometres east of San Francisco Bay, it's at the northern tip of San Joaquin Valley and gained approval in 1986. This is one of California’s largest AVAs; the space spans more than 200,000 hectares, with 42,000 under vine, contributing 20% of California’s total production. The area is planted to more than 120 varieties and is home to several very old vineyards, with Zinfandel, Carignan and others going back over 100 years in many cases. This inland region is dominated by sand- and clay-based soils and enjoys a Mediterranean climate characterised by warm, dry summers and cool, wet winters. The diurnal range is less exaggerated than in some of the neighbouring AVAs. Its seven official sub-regions are Alta Mesa, Borden Ranch, Mokelumne River, Cosumnes River, Jahant, Sloughhouse, and Clements Hill.