Native American Navajo rugs represent the native American Indian contribution to the world of textile production. The origins of Navajo weaving, however, are difficult to trace back before the late nineteenth century. The oldest surviving instances of Navajo weaving date back to 1805. Sheep wool was first introduced by the Spaniards several hundred years ago, but Navajo rug and blanket production only seems to have begun after American control was established. Many of the designs were supplied by Caucasian American entrepreneurs, sometimes using Oriental tribal rug patterns. Navajo carpets that have vegetable dyes predating the introduction of industrial synthetics are also most desirable.