Oregon Archaeology

Chapter 5: The Willamette Valley

284 Chapter 5 The Willamette Valley Physical Setting A large portion of the modern Willamette Valley floor was formed near the end of the last ice age, between about 20,000 and 15,000 cal. BP, when glacial Lake Missoula, impounded by a lobe of the Cordilleran ice sheet, repeatedly breached its ice dam and sent floods of enormous scale down the Columbia River valley to the Pacific Ocean. The constricted river channel at Kalama Gap, below the Portland Basin, temporarily caused the flow to back-flood to the southern end of the Willamette Valley. The sediment that settled from these temporarily stilled floodwaters of the “Willamette Sound” formed an undulating plain with pothole lakes, marshes, and bogs. The modern Willamette River and its tributaries negotiated their courses across this new surface. About 20 miles wide and 100 miles long, the Willamette Valley is flanked east and west by the coniferous forests of the Cascades and Coast ranges. Prior to twentieth century agricultural land clearing, gallery forests of deciduous and evergreen trees followed the watercourses, and most of the valley floor was open grassland with scattered groves of oak (Towle 1982; Boyd 1999). The earliest writings of the valley describe an idyllic scene; Robert Stuart, an employee of John Jacob Astor’s Pacific Fur Company, reported in 1811 that the valley was “delightful beyond expression,” one of “the most beautiful Landscapes in nature” (Rollins 1935:32). Modern botanists acknowledge that the Willamette Valley landscape described by early trappers and farmers was anthropogenic, created and maintained by Native people using judicious controlled burning (Boyd 1999; Johannessen et al. 1971; Lewis 1990; Towle 1979). In describing the Willamette prairie in 1845, James Clyman (1960:121) recorded that he “walked out over a fine rounded ridge covered with green grass now springing up Beautifully and haveing [sic] the appearance of wheat fields in the THE WILLAMETTE VALLEY 285 states at this season of the year.” While some early explorers complained that the extensive burning of the valley floor left them inadequate forage for their horses at some times of the year, others commented on the “wheat field”-like appearance of Oregon’s western valleys (Applegate 1914:69; Riddle 1953:51; Church 1951:11); this is likely the product of intentional burning which fostered the growth of even-aged stands of seed-bearing annual plants. The bordering forests also bore the evidence of active maintenance; Charles Wilkes (1845:358) noted in 1841 that “This part of Willamette Valley is a prolonged level, of miles in extent circumscribed by the woods, which have the appearance of being attended to and kept free from undergrowth. This is difficult to account for, except for the agency of fire destroying the seeds. . . . That this is the case appears more probable from the fact that since the whites have had possession of the country [and discontinued the annual burning practiced by the Indians], the undergrowth is coming up rapidly in places.” Annual burning greatly enhanced food production in the valley; frequent burning favors the growth of certain plants over conifers and shrubs, including seed-bearing annuals and grasses, geophytes such as camas, and fire-tolerant species such as oaks—all staple foods for the Native Kalapuya. Fire was also used to manage some shrubby plants in multi-year burning cycles, such as Fig. 5.1. Kalapuya language and dialect communities documented in the mid nineteenth century (left) and location of key archaeological sites (right). 286 OREGON ARCHAEOLOGY hazel (important both for nuts and basketry materials), huckleberries, and other economic plants (Anderson 1990, 1993; Lewis 1973, 1990). Cultural Setting At the opening of the nineteenth century, Kalapuyan speakers occupied all of the Willamette Valley above the falls at Oregon City, as well as the northernmost tributary drainages of the Umpqua basin to the south (fig. 5.1). Based on texts recorded by linguists between the late 1880s and early 1900s, the Kalapuyan language family was found to include three languages and at least 13 dialects. This diversity suggests both “a long antiquity of residence in the valley” (Jacobs 1937:66) and a relatively settled populace. Each dialect community included a group of villages occupying the major tributary streams. These multi-village communities correspond to the commonly identified Kalapuya group names, many of which survive today in the names of the river basins they occupied, such as the Tualatin, Yamhill, Santiam, Luckiamute, and others. Other group names are known...