People in what is now Washington State were smoking Rhus glabra, a plant commonly known as smooth sumac, more than 1,400 years ago. The discovery, made by a team of Washington State University researchers, marks the first-time scientists have identified residue from a non-tobacco plant in an archeological pipe. Unearthed in central Washington, the Native American pipe also contained residue from N. quadrivalvis, a species of tobacco not currently grown in the region but that is thought to have been widely cultivated in the past. Until now, the use of specific smoking plant mixtures by ancient people in the American...