"Over the Wilson River Highway from its junction with the Oregon Coast Highway, US101, in Tillamook, easterly via Glenwood to its junction with the Sunset Highway, US26, at Tillamook Junction, approximately three and one-half miles west of North Plains."
~ ODOT, Descriptions of US and Oregon Routes, March 2007
OR-6 was designated in 1942, but the highway that it is associated with actually has existed since 1935. The Wilson River Highway, at that time, was a proposed highway that ran from Tillamook to somewhere near Banks; however, at that time, only a little spur outside of Tillamook. By 1942, the highway was complete from Tillamook to Glenwood, and the only portion that remained was between Gales Creek and the then-under construction Wolf Creek Highway #47 (currently US-26). So, in the interim, OR-6 was placed on Gales Creek Rd. from Gales Creek to Forest Grove and duplexed with OR-2 on the Tualatin Valley Highway from Forest Grove to Portland. When OR-2 was moved onto the newly completed Sunset Highway, OR-6 remained from Forest Grove to Sylvan (presumably rolled back from Portland). Finally, the last segment of the Wilson River Highway was completed from Gales Creek to Banks Jct., and OR-6 was moved onto it in 1957.
What was OR-6 between 1942 and 1957 is still completely intact and is shown in red. The portion of OR-6 from Gales Creek to Sylvan survives today as OR-8, and the portion from Sylvan to the Portland City Limits (Exit 73) is currently US-26. The portion within Portland's City Limits is the Jefferson-Columbia St. couplet, and that has been turned over to Portland for maintenance; it is no longer part of the state highway system.