"Over the Swift Highway from its beginning at the Union Pacific Railroad overcrossing on N. Portland Road in Portland, thence northeasterly to N. Marine Drive, thence southeasterly to the end of the Swift Highway at the Swift-Union Interchange with Pacific Highway East, OR99E, and Pacific Highway, I-5, in north Portland. (Est. 7/24/2002)"
~ ODOT, Descriptions of US and Oregon Routes, March 2007
OR-120 was designated in July 2002 when the Oregon Transportation Commission decided to start giving route numbers to all of Oregon's unmarked state-maintained highways. OR-120, a 2.71-mile highway that begins at I-5 and ends abruptly in the St. Johns area of Portland, was numbered after its corresponding highway designation, Swift Highway #120. It mainly services Port of Portland and industrial traffic, but other than that, it serves no useful purpose and, in my opinion, should be dropped from the state highway system entirely. I have reason to believe that the remaining Swift Highway is a remnant of a much longer Swift Highway that was shortened for some reason; I will investigate this further. I travelled this highway in March of 2004, and thus far no OR-120 signs have been placed in either direction; drivers on the highway are instead directed towards I-5.