The Maryhill Museum located near Goldendale, Washington, has a display of Plateau flat bags. The Plateau Culture Area is the area between the Cascade Mountains and the Rocky Mountains in Washington, Oregon, Idaho, British Columbia, and Western Montana. From north to south it runs from the Fraser River in the north to the Blue Mountains in the south. Much of the area is classified as semi-arid. Part of it is mountainous with pine forests in the higher elevations.
Among the baskets made by the Plateau people was a flat storage bag. This bag was insect-resistant, dust-tight, and expandable. It was often used for storing dried roots. In her book Columbia River Basketry: Gift of the Ancestors, Gift of the Earth, Mary Dodds Schlick writes:
“The soft sack-like shape flattens for storage and holds great quantities when filled.”
According to the Museum display:
“Flat twined bags made of native hemp and cornhusk were traditionally used throughout the Plateau to store and carry roots and root cakes. These large, durable bags were woven in natural sheds of brown, yellow, and green, and usually closed with a drawstring.”