 Following the end of Prohibition, Washington's fledgling wine industry was based primarily on fortified sweet wine production made from the "Vitis labrusca" variety Concord.The Nawico and Pommerelle wineries were the most widely recognized producers, making millions of gallons each year of sweet jug wine made from Concord and other varieties.In the 1950s, the planting of "Vitis vinifera" saw an increase spearheaded, in part, by the work of Dr. Walter Clore and Washington State University which conducted a series of trials on which grape vines could produce the best wine in various soils and climates of Washington.