Former US-99W (current OR-99W)
NE Eads St.
NE 3rd St., NE Yaquina Heights Dr., and Old Corvallis-Newport Highway
(within and outside Newport)
Fruitvale Ln., Tom Jack Rd., and McNary Ln.
(between Newport and Toledo)
Neal Loop and Powell Mountain Loop
(outside of Toledo)
Western Blvd., SW Washington St., SW 2nd St., and NW 2nd St.
OR-26 was created with the advent of the state highway system in 1932 and ran from Newport to Albany by way of Toledo, Philomath, and Corvallis along the Corvallis-Newport Highway #33 from Newport to Corvallis and the Albany-Corvallis Highway #31 between Corvallis and Albany. Within Corvallis, OR-26 was cosigned with US-99W (the West Side Pacific Highway #3 from 1932-1939, West Side Pacific Highway #1W from 1939 on) for about a block. In 1940, US-20 was knocking on OR-26's door after being extended to Albany, and sure enough, in 1945, OR-26 was formally retired, dropped in lieu of a US-20 extension to the coast. The 26 route designation would return, however, with the extension of US-26 in Oregon along US-28, OR-27, OR-50, and OR-2.
There are many old alignments of OR-26 that have survived through time, the first instance of this is a group of disjointed sections between Newport and the near-coastal city of Toledo. This section of OR-26 (shown in red) was in use from 1917 (at the inception of the Oregon State Highway System) until sometime after 1945, when OR-26 was replaced by US-20. It is mostly intact with a few sections that have been closed or taken out, most likely for safety concerns. To follow the old route, take US-20 east from US-101 in Newport and turn left onto NE Eads St., then go three blocks north and turn right onto NE 3rd St. This road will turn into NE Yaquina Heights Dr. and then the Old Corvallis-Newport Highway. Continue to its end at Steenson Rd., veering right until you reach US-20; turn east (left). Then, take a left on another road, View Ridge Ln., which will soon connect to another disjointed section of the Old Corvallis-Newport Highway. After this point, the exact point of the route gets a little fuzzy; I believe that parts of old OR-26 survive as Fruitvale Ln., Tom Jack Rd., and McNary Ln., and I am unsure of the routings between each section. The current highway, in any place that the red section parallels, was never OR-26 at any time.
This section of OR-26 through Toledo (shown in green) was in use from 1917 until 1971, well after OR-26's elimination from the highway. It has since re-entered the state highway system as the Corvallis-Newport Highway #33AA Toledo Frontage Road, better known as US-20 Business; it does have its own mileage attached to it, but none are marked by mileposts.
These sections of OR-26 through Toledo (shown in blue) were in use from 1917 until sometime after 1945, when they were bypassed by US-20's current routing. The first section, called the Neal Loop, may or may not have been a section of the old highway, but the second section, the Pioneer Mountain Loop, was; I confirmed it in an old US Geological Survey map of the area. I just need to look at the map again and make some better comparisons, but I'm fairly confident both existed as part of an early US-20/OR-26.
Another portion of former highway that still is entirely intact is OR-26's previous alignment through Corvallis. This route, shown in gold, was a part of the Corvallis-Newport Highway from 1917 to 1962, when the bypass to the south of Corvallis was completed (long after OR-26's removal from the Oregon route system). Through then, US-20 was routed through Corvallis on Western Blvd. until SW 3rd St. (then US-99W), followed US-99W for a block, turned east onto SW Washington St. for another block, and then followed SW/NW 2nd St. out of town on the Albany-Corvallis Highway #31.