AMP: Umatilla Mission Hwy #331/0 Location: Umatilla Mission Hwy and OR 11, Umatilla Cty No reassurance shield as Oregon 331 begins. 331 is definitely the most significant unsigned highway in eastern Oregon, serving as the main route from I-84/La Grande up to Milton-Freewater/Walla Walla and points further into Washington. AMP: 2 Location: Umatilla Mission Hwy and Mission … Continue reading Oregon Route 331, OR 11 to I-84/US-30