UP used and uses the Oregon-Washington Railway and Navigation Railway line along the south bank of the Columbia. The line splits east of Portland with passenger trains following a line which today is pretty much followed by I-84 and Tri-Max to Union Station. The line to Seattle was party shared with NP and GN
Because the line up the Columbia from Portland is relatively flat UP's smaller and mid-sized power such as Pacifics and Mikados predominated. Hinkle Oregon was where the grades started and an engine change point where heavier power could be found.