The Wahluke Slope AVA was established in 2006 and produces, on average, around 20% of the state's wine grapes. Of the region's , nearly were planted as of 2008. Located among the foothills south of the Saddle Mountains, the Wahluke Slope is one of the warmest and driest regions in the state. The Columbia River forms the western and southern boundaries of the AVA with the Hanford Reach National Monument bordering the appellation on the east. The vintage characteristics of Wahluke slope are very consistent year to year due to the area's reliably dry, warm climate and uniform coarse gravelly sand soils that drain water well. More than three-quarters of the area's production is in red wine grapes—particularly Merlot, Cabernet Sauvignon and Syrah. As of 2007, more than 50 wineries purchased grapes from the Wahluke Slope, with many of them featuring the AVA or one of its 20 vineyards on wine labels.