A hilly tract of land on the Columbia River's north slope in Washington State, affectionately called the Horse Heaven Hills, will be the state's seventh federally recognized wine grape-growing region.Known as American Viticultural Areas or appellations, such designations recognize a region's distinct climate and soil features.Wineries and grape growers in the 570,000-acre Horse Heaven Hills submitted an application for recognition in 2002. The U.S. Treasury Department's Alcohol and Tobacco Tax and Trade Bureau approved the appellation request, effective Aug. 1.Such approval is a significant achievement for the state's wine industry, because it allows vintners to distinguish wines produced in the region and allows consumers to easily identify those wines, said Robin Pollard, executive director of the Washington Wine Commission, a promotional state agency funded by fees on member wineries and growers.The recognition also speaks to the degree of development and sophistication of Washington's wine industry, she said."Diversity, that is really one of our state's greatest assets," she said. "It just gives us yet another tool to help raise awareness in terms of what makes Washington wines so special."Washington state is the nation's second-largest producer of wine, after California. More than 300 wineries, 300 wine grape growers and 30,000 vineyard acres support the $2.4 billion annual industry.The federal government already has recognized the state itself as an appellation.Its warmer temperatures than some areas of the state, such as the Yakima Valley appellation, make the Horse Heaven Hills ideal for such varieties as merlot and cabernet sauvignon. At the same time, vintners are finding success with some white wine varieties as well, such as chardonnay and riesling, said Kevin Corliss, director of viticulture for Ste. Michelle Wine Estates.