US 10 (trunk)

Seattle to Teanaway

Seattle to Issaquah

US 10 originally began at Jct US 99 on the south side of downtown Seattle at the intersection of 4th Ave S and Airport Way. From this intersection, US 10 headed SE for a block to S Dearborn St, then east on Dearborn to Rainier Ave S. When US 99 was rerouted past downtown via the Alaskan Way Viaduct in the mid 1950s, US 10 was extended northerly via former US 99, later Business US 99, to Jct US 99 at the north end of the Battery St tunnel near the intesection of Aurora Ave N and Denny Way.

From Dearborn, US 10 headed southerly on Rainier Ave via the Rainier Valley to Renton. In the early 1930s, Empire Way (now Martin Luther King Jr Way) was built from the Rainier Valley west of Rainier Ave to Renton. US 10 was shifted to Empire Way. Rainier Ave from the Rainier Valley to Renton was dropped from the state highway system at this time but added back in 1937 as a northern extension of PSH 5.

From Renton to Issaquah, US 10 followed the Renton-Issaquah Rd. Through downtown Issaquah US 10 used Sunset Way.

The first Lake Washington floating bridge opened to traffic in July 1940. US 10 was shifted to the floating bridge route from Seattle via Mercer Island to the east side of Issaquah. At Issaquah, US 10 was shifted from Sunset in downtown to a new route north of downtown that today is Gilman Blvd. Former US 10 around the south end of the lake via Renton became Alternate US 10.

Issaquah to North Bend

US 10 headed east from Issaquah to Preston. The original roadway was replaced by a 4 lane road after the floating bridge was completed. This 4 lane road in turn was replaced by the 6-7 lane I-90 in the early 1970s. From Preston, US 10 originally headed north to Fall City. From Fall City to North Bend, US 10 followed the road that is today SR 202. In the early 1940s, a 4 lane US 10 was built on a more direct route from Preston to North Bend. This road was incorporated into I-90 from Preston to the west outskirts of North Bend.

North Bend to Snoqualmie Pass

I-90 was built on top of US 10 much of the way from North Bend to Snoqualmie Pass. Starting out from downtown North Bend, old US 10 still exists most of the way to Exit 34. Old US 10 is still a separate road to the south of I-90 in the vicinity of Exit 38. From the Denny Creek area to Exit 52, old US 10 runs up the middle of the two widely spaced sides of I-90. in the late 1920s and early 1930s, US 10 was shifted to two lanes of what is now eastbound I-90. Two more lanes were added to old US 10 from North Bend to Exit 52 in the early 1950s. At exit 52, I-90 and old US 10 split. Old us 10 is now SR 906 across Snoqualmie Pass and downhill to Hyak. I-90 is to the north. The two rejoin at Exit 54.

Snoqualmie Pass to Teanaway

US 10 ran along the northeast side of Keechelus lake in a southeasterly direction towards Easton. A snowshed was added in the early 1950s and the highway was widened to 4 lanes in stages by the late 1950s. US 10 originally passed through the community of Easton. The Easton bypass that became I-90 was built around 1959. The 2 lane highway from Easton to Bullfrog Flats (I-90 Exit 80) became one side of the 4 lane divided I-90 freeway in the early 1960s. US 10 originally crossed the Cle Elum River on a bridge upstream from the I-90 twin bridges. The earlier of the I-90 spans was built in the 1950s and paralleled around 1962. Old US 10 through downtown Cle Elum became signed as Business Loop 90 after the I-90 Cle Elum bypass opened in 1967. There was still at least one Business Loop 90 sign in Cle Elum as late as 2003. US 10 continued easterly to the present junction of SR 970 and SR 10 at Teanaway.

From 1926 to 1940, US 10 headed north from Teanaway and crossed (Old) Blewett Pass to the Big "Y" near Peshastin, then easterly via Wenatchee, Waterville, Coulee City, Wilbur, and Davenport to Spokane. In 1940, US 10 was rerouted via Ellensburg, Vantage, Moses Lake, Ritzville, and Cheney to Spokane.