It is located in the Willamette Valley where the Calapooia River and the Willamette River meet . it is in both Linn and Benton Counties , just east of Corvallis and south of Salem Oregon . It is located in the Willamette Valley at the confluence of the Calapooia River and the Willamette River in both Linn and Benton counties , just east of Corvallis and south of Salem .