far south as Eugene. The floodwaters carried rich volcanic and glacial soil from Eastern Washington, which was deposited across the valley floor when the waters subsided. The soil in the Willamette Valley is about deep in some areas. In the cool moist climate of the Willamette valley, over 170 different crop and livestock items are produced, including grass and legume seeds, tree fruits and nuts, wine grapes, berries, vegetables, nursery, Christmas trees, and field crops such as wheat, oats, mint and hops, hay, livestock and poultry and miscellaneous field crops. The valley produces most of the cool-season forage and turf grass, Christmas trees, and hazelnuts sold in North America. It is also noted for its hops, which are widely used in craft beer and microbreweries throughout the U.S. In recent decades, the valley has also become a major wine producer, with multiple American Viticultural Areas of its own. With a cooler climate than California, the gently rolling hills surrounding the Willamette are home to some of the best (and most expensive) Pinot noir in the world, as well as a high-quality Pinot gris. Although this distinction is not officially recognized, many wine connoisseurs further divide the Willamette Valley into northern and southern regions, the dividing line being the approximate latitude of Salem (approximately 45° north latitude). Not all portions of the Willamette Valley are suitable for vineyards, however, and the largest concentration of wineries is found west of the Willamette River, on the leeward slopes of the Coast Range, or among the numerous river and stream valleys created by Willamette River tributaries. By far, the largest concentration of wineries is in Yamhill County. Grass farmers have been burning fields, as part of their production, since the 1940s. The smoke is often irritating to residents; in 1988 it caused a 23-car pileup on I-5. Over the years, several pieces of legislation have limited the amount of burning permitted. With the passage of a bill championed by legislator Paul Holvey in the 2009 session, burning has been banned since the summer of 2010, with the exception of an area of about with steep terrain and certain species. (At its peak in the 1980s, about were burned each year.) The marionberry, a cross between Chehalem and Olallie blackberries, was bred at Oregon State University as part of a berry-developing partnership with the U.S. Department of Agriculture that dates back to the early 1900s.