Interstate 90 in Washington

Interstate 90
Interstate 90 is highlighted in red
Route information
Maintained by WSDOT
Length:	296.92 mi[1][2] (477.85 km)
Tourist routes:	Mountains to Sound Greenway - I-90
Major junctions
West end:	I‑5 / SR 519 in Seattle
	I‑405 in Bellevue I‑82 / US 97 near Ellensburg US 395 near Ritzville US 2 in Spokane US 195 in Spokane
East end:	I-90 at Idaho state line
Location
Counties:	King, Kittitas, Grant, Adams, Lincoln, Spokane
Highway system
Interstate Highway System Main Auxiliary Suffixed Business State Highways in Washington Interstate US State Scenic Former PSH 1964 renumbering Former ← I‑82 SR 92 →

Interstate 90 (I-90), a transcontinental Interstate Highway from Seattle, Washington, to Boston, Massachusetts, crosses the state of Washington before crossing the Idaho state line between Spokane and Post Falls. It serves the cities of Seattle, Bellevue, Issaquah, Ellensburg, Moses Lake, Ritzville, and Spokane.^[3][4]

It is the only Interstate Highway to cross the state east to west, but there are two U.S. Routes that also do the same, U.S. Route 2 and U.S. Route 12, along with a few state highways.^[5][6] I-90 is also the only highway in Washington to connect the two largest cities in the state (Seattle and Spokane).^[7][8] The road is the third busiest in the state, behind I-5 at 240,000^[9] and I-405 at 201,000.^[9] An estimated 148,000 motorists use the road daily.^[9]

I-90 incorporates two of the longest floating bridges in the world, the Lacey V. Murrow Memorial Bridge and the Homer M. Hadley Memorial Bridge, which cross Lake Washington from Seattle to Mercer Island, Washington. They are the second- and fifth-longest such bridges, respectively.

Route description

Seattle to Snoqualmie Pass

I-90 in Seattle and Vicinity

Interstate 90 starts at the intersection of SR 519 and 4th Ave S in Downtown Seattle. The recently rebuilt freeway joins the I-90 Express Lanes and goes east to an interchange with I-5. After leaving the interchange, the highway travels through the Central Area and into the Mount Baker Tunnel, a tunnel on the National Register of Historic Places^[10] that carries I-90 and its express lanes under the Mount Baker neighborhood. After emerging from the eastern portal of the tunnel, I-90 splits and the eastbound lanes go on the Lacey V. Murrow Memorial Bridge and the westbound lanes exit off the Homer M. Hadley Memorial Bridge, which is shared with the I-90 express lanes, both over Lake Washington.^[11]

After crossing Lake Washington into an area known as "the Eastside", I-90 enters Mercer Island and goes under the Mercer Island Lid at West Mercer Way and emerges at 76th Avenue SE before^[12] leaving Mercer Island to cross over Lake Washington again on the shorter East Channel Bridge into the city of Bellevue. The freeway continues east, passing an interchange with Bellevue Way, where the express lanes end, before a large stack interchange at I-405 near the Factoria Mall.

The freeway travels through the Eastgate area of Bellevue and passes Bellevue College, Lake Sammamish, and Lake Sammamish State Park before entering Issaquah and intersecting SR 900.^[13][14]

After passing by downtown Issaquah, the highway goes along the northern boundary of the Tiger Mountain State Forest and passes Preston, where the speed limit raises from 60 MPH to 70 MPH, before intersecting SR 18 in Upper Preston. From Upper Preston, I-90 passes Echo Lake and Snoqualmie before entering North Bend, where SR 202 begins after an interchange with the highway.^{[15][16][17][18]}

Seattle-Bellevue Express Lanes

I-90 and its express lanes (middle) go east across Lake Washington on the Lacey V. Murrow Memorial Bridge and Homer M. Hadley Memorial Bridge.

Interstate 90 has a 7.45-mile (11.99 km) long^[2] reversible express lane that goes across Lake Washington from Seattle to Bellevue. The express lane starts at two different locations, one at the southern terminus of the Downtown Seattle Transit Tunnel and the other at a signalled intersection at 5th Avenue S., S. Dearborn Street, and Airport Way S. The lanes turn east and travel in a separated right-of-way before traveling towards the middle of I-90 east of the interchange with I-5. This section is bi-directional, containing two lanes separated by a barrier, and allows buses to use the lanes in both directions at all times. From there, the lanes travel through the Mount Baker Tunnel and onto the Homer M. Hadley Memorial Bridge, sharing the bridge with the westbound lanes. From there, the lanes travel through Mercer Island and ends at its terminus with the I-90 interchange with Bellevue Way, with ramps connecting to mainline I-90 and I-405.^{[11][13][19][20]}

Segments of the express lanes between the western terminus and I-90 ramps and Island Crest Way and the eastern terminus are reserved for HOV only. The westbound traffic uses the express lanes from 1 am to 12:30 pm (Monday–Friday) The eastbound traffic uses the express lanes from 2 pm to 12 midnight (Monday–Friday) and all day from Saturday to Sunday. The express lanes are closed every other Tuesday from 10 am to 1:30 pm.^[21]

Snoqualmie Pass to Ritzville

I-90 crossing over the Columbia River on the Vantage Bridge near Vantage.

Around 42 miles east of Bellevue, at milepost 53, I-90 traverses the Cascade Mountains via Snoqualmie Pass, elevation 3,022 feet (921 m), the only interstate crossing and lowest east–west crossing in Washington State.^[22] I-90 then goes out towards the Columbia Plateau, passing through the cities of Cle Elum and Ellensburg, where it intersects with Interstate 82. It crosses the Columbia River on the Vantage Bridge. After passing into Grant County, North Frontage Road and South Frontage Road parallel I-90 through Grant County. The frontage roads intersect each exit off I-90 (Exits 143 to 174 and Exits 179 to 184). In Moses Lake at Exit 174, the frontage roads end. The freeway passes through Moses Lake. The frontage roads begin again at Exit 179 in Moses Lake and end at the Adams County line.^{[16][18][23][24][25]}

Ritzville to Idaho

I-90 as seen from the parking lot of Deaconess Medical Center in Spokane.

At Ritzville, I-90 forms a concurrency with US 395 towards Spokane, where US 2 also forms a concurrency and both US 395 and US 2 branch off from I-90 at Downtown Spokane. I-90 continues to head east through the suburbs of Spokane and into Idaho.^{[16][26][27][28][29][30][31]}

History

As part of the state's first connected state highway system, the Washington State Legislature designated the Sunset Highway between Seattle and Idaho in 1913.^[32][33] Later in 1915, the Legislature also designated the North Central Highway between Ellensburg and Davenport.^[32] The State Highway Board selected two routes that would partially connect the main cities of Western Washington to Eastern Washington and Idaho.^[34][35] In 1923, by which time the entire road had been improved and a new connection had filled in a small gap,^[36] the Sunset Highway became State Road 2 (Primary State Highway 2 after 1937), but retained its name.^[37] The North Central Highway became State Road 7 (Primary State Highway 7 after 1937), but retained its name.^[37] Another highway, named Primary State Highway 18 between George and Ritzville.^[38] By that time, most of the route of Interstate 90 became US 10, which was established in 1926.^[39][40][41] Until 1940, the route headed south from Seattle to Renton, then east to Issaquah, in order to travel around Lake Washington.

Interstate 90 crosses Lake Washington between Seattle and Bellevue on a pair of floating bridges that are two of the world's longest floating bridges. The westbound lanes travel on the Homer M. Hadley Memorial Bridge, the fifth longest floating bridge, and the eastbound lanes travel on the Lacey V. Murrow Memorial Bridge, the second longest floating bridge. The Lacey V. Murrow Memorial Bridge, originally called the Lake Washington Floating Bridge, opened on July 2, 1940.^[42] The bridge sank during construction on November 25, 1990. It was later rebuilt and the new bridge opened later in 1993.^[43][44] The second bridge, the Homer M. Hadley Memorial Bridge, opened on June 4, 1989.^[43]

The new terminus of Interstate 90 after the first phase of the project.

Later in 1956, President Dwight D. Eisenhower signed the Federal-Aid Highway Act of 1956 which started the construction of Interstate Highways.^[45][46] By 1969, US 10 was removed from the system entirely. During the construction of the freeway between Seattle and Bellevue, lawsuits were filed on May 28, 1970 and stopped construction of Interstate 90 until the early 1990s.^[43][47] Legally, the Washington section of I-90 is defined at Washington Revised Code § 47.17.140.^[48] In 1998, I-90 from Seattle to Thorp was designated the Mountains to Sound Greenway to protect its outstanding scenic and cultural resources.^[49]

Before 2003, Interstate 90 used to end at a signalled intersection with 4th Avenue S. However, increasing traffic from Downtown Seattle, Colman Dock, Safeco Field, and Qwest Field forced city, county, and state officials to look for improvements to the area. The first stage of the improvements, the SR 519 South Seattle Intermodal Access Project, included the construction of a new on-ramp to Interstate 90 via a new interchange with 4th Avenue S. and Edgar Martínez Drive S. (formerly S. Atlantic Street). Other projects are currently ongoing and have been completed in the recent years on I-90.^[50]

Exit list

County	Location	mi[2]	km	Exit	Destinations	Notes
King	Seattle	0.00	0.00	1A	Edgar Martínez Drive South, South Atlantic Street	Westbound exit and eastbound entrance
		0.00	0.00	1B	SR 519 north / 4th Avenue South  – Seattle City Center, Amtrak, Ferries, Safeco Field, CenturyLink Field	Westbound exit and eastbound entrance; national western terminus; I-5 south exit 164, north exit 164B
		0.32	0.51	2	I‑5 – Vancouver, Tacoma, Portland	Signed as exits 2A (south) and 2B (north) eastbound and 2B (south) and 2C (north) westbound; I-5 south exit 164, north exit 164A
		1.39	2.24	3	Rainier Avenue	Signed as exits 3A (south) and 3B (north) westbound; no westbound entrance
		1.58	2.54	—	Express Lanes	Eastbound exit and westbound entrance
	Lake Washington	2.13	3.43	Lacey V. Murrow Memorial Bridge and Homer M. Hadley Memorial Bridge
	Mercer Island	4.09	6.58	6	West Mercer Way	Eastbound exit and westbound entrance
		4.91	7.90	7A	77th Avenue Southeast	Eastbound exit and westbound entrance
		5.02	8.08	—	80th Avenue Southeast	HOV only; westbound exit and eastbound entrance
		5.17	8.32	7B	Island Crest Way	Signed as exit 7 westbound
		6.38	10.27	—	Express Lanes	Westbound exit and eastbound entrance
		6.41	10.32	8	East Mercer Way
	Lake Washington	6.78	10.91	East Channel Bridge
	Bellevue	7.19	11.57	9	Bellevue Way
		7.98	12.84	10A	I‑405 – Everett, Renton	Signed as exit 10 westbound; I-405 exit 11
		8.23	13.24	10B	Richards Road – Factoria	Eastbound exit and westbound entrance
		9.09	14.63	—	142nd Place Southeast	HOV only
		9.60	15.45	11B	148th Avenue Southeast – Bellevue College	Westbound exit is via 156th Avenue
		9.60	15.45	11A	150th Avenue Southeast, 156th Avenue Southeast	Signed as exit 11 westbound
				11	161st Avenue Southeast	Eastbound exit is via 150th Avenue
		11.73	18.88	13	West Lake Sammamish Parkway, Lakemont Boulevard Southeast, Southeast Newport Way
	Issaquah	13.89	22.35	15	SR 900 west (17th Avenue Northwest) – Renton
		15.20	24.46	17	Front Street, East Lake Sammamish Parkway Southeast
		16.13	25.96	18	East Sunset Way, Highlands Drive
		18.32	29.48	20	High Point Way
		20.59	33.14	22	Preston, Fall City
		23.72	38.17	25	SR 18 west / Snoqualmie Parkway – Auburn, Tacoma
		25.40	40.88	27	Snoqualmie, North Bend	Eastbound exit and westbound entrance
	North Bend	28.63	46.08	31	SR 202 west – North Bend, Snoqualmie
		30.95	49.81	32	436th Avenue Southeast
		33.06	53.20	34	468th Avenue Southeast
		36.14	58.16	38	—	Eastbound exit and westbound entrance
		37.96	61.09	38	—	Westbound exit and eastbound entrance
		40.68	65.47	42	Tinkham Road
		43.91	70.67	45	USFS Road 9030
		46.09	74.17	47	Denny Creek, Asahel Curtis
	Snoqualmie Pass	50.58	81.40	52	SR 906 – West Summit, Alpental	Eastbound exit and westbound entrance
Kittitas		51.29	82.54	53	East Summit, Snoqualmie Pass Recreational Area
		53.03	85.34	54	SR 906 – Hyak, Gold Creek	Access to SR 906
		61.30	98.65	62	Stampede Pass, Lake Kachess
		62.31	100.28	63	Cabin Creek Road
		68.63	110.45	70	Sparks Road – Easton
		69.85	112.41	71	Easton
		72.34	116.42	74	West Nelson Siding Road
		76.35	122.87	78	Golf Course Road
		78.60	126.49	80	Roslyn, Salmon la Sac
	Cle Elum	81.41– 82.49	131.02– 132.75	84	Cle Elum, South Cle Elum
		84.15	135.43	85	SR 903 north / SR 970 – Cle Elum, Wenatchee
		91.91	147.91	93	Elk Heights Road
		99.36	159.90	101	Thorp Highway – Thorp
		104.35	167.94	106	US 97 north – Ellensburg, Wenatchee	West end of US 97 overlap
	Ellensburg	107.65	173.25	109	I‑90 Bus. (Canyon Road) – Ellensburg
		109.15	175.66	110	I‑82 east / US 97 south – Yakima	East end of US 97 overlap
		113.76	183.08	115	Kittitas
		134.72	216.81	136	Huntzinger Road – Vantage
Columbia River		135.72	218.42	Vantage Bridge
Grant		136.08	219.00	137	SR 26 east to SR 243 – Othello, Pullman, Richland
		139.65	224.74	139	Scenic View
		142.14	228.75	143	Silica Road
		148.07	238.30	149	SR 281 north – Quincy, Wenatchee, George
		150.02	241.43	151	SR 283 north / SR 281 north (via SR 281 Spur) – Ephrata, Soap Lake, Quincy, Wenatchee
		152.90	246.07	154	Adams Road
		162.88	262.13	164	Dodson Road
		167.96	270.31	169	Hiawatha Road
	Moses Lake	172.89	278.24	174	Hansen Road – Mae Valley
		173.69	279.53	175	Westshore Drive – Mae Valley	Westbound exit only
		174.28	280.48	176	I‑90 Bus. east / SR 171 north – Moses Lake
		177.74	286.04	179	SR 17 / I‑90 Bus. west – Moses Lake, Ephrata, Othello
		181.12	291.48	182	O Road Northeast/Southeast – Wheeler
		183.18	294.80	184	Q Road Northeast/Southeast
		187.18	301.24	188	U Road Northeast/Southeast – Warden
Adams		195.20	314.14	196	Deal Road – Schrag
		205.13	330.12	206	SR 21 – Lind, Odessa
		213.52	343.63	215	Paha, Packard
		218.21– 218.49	351.17– 351.63	220	US 395 south – Ritzville, Pasco	Western end of US 395 overlap
		219.67	353.52	221	SR 261 south – Ritzville, Washtucna
		224.14	360.72	226	Schoessler Road
		228.95	368.46	231	Tokio
Lincoln	Sprague	242.98	391.04	245	SR 23 – Sprague, Harrington
		251.74	405.14	254	Fishtrap
Spokane		255.41	411.04	257	SR 904 east – Tyler, Cheney
		262.02	421.68	264	SR 902 east – Cheney, Medical Lake
		268.27	431.74	270	SR 904 west – Four Lakes, Cheney
		270.53	435.38	272	SR 902 west – Medical Lake
		274.04	441.02	276	I‑90 Bus. east – Spokane, Geiger Field
		275.45	443.29	277B	US 2 west – Spokane Airport, Fairchild AFB, Davenport	Western end of US 2 overlap; signed as exit 277 westbound
		275.92	444.05	277A	Garden Springs	Signed as exit 277 westbound; no entrance ramps
	Spokane	277.06	445.88	279	US 195 south – Colfax, Pullman
		277.88	447.20	280A	Maple Street	Signed as exit 280 eastbound
				280B	Lincoln Street	Eastbound exit is via exit 280
		279.05	449.09	281	US 2 east / US 395 north (Division Street) – Newport, Colville	Eastern end of US 2/US 395 overlap
		279.83	450.34	282A	SR 290 east (Trent Avenue) / Hamilton Street	Signed as exit 282 eastbound
		280.08	450.75	282B	Second Avenue	Westbound exit only
		280.74	451.81	283A	Altamont Street
		281.44	452.93	283B	Thor Street, Freya Street
	Spokane–Spokane Valley city line	282.05	453.92	—	Havana Street	Eastbound entrance only
	Spokane Valley	283.32	455.96	285	Sprague Avenue	No eastbound entrance
		283.95	456.97	286	Broadway Avenue
		285.54	459.53	287	Argonne Road
		287.56	462.78	289	SR 27 (Pines Road)
		288.74	464.68	291A	Evergreen Road – Spokane Valley Mall
		289.62	466.10	291B	Sullivan Road
		291.66	469.38	293	Barker Road
	Liberty Lake	292.63	470.94	294	Country Vista Drive, Appleway Avenue	Westbound exit and eastbound entrance
		293.89	472.97	296	Liberty Lake, Otis Orchards
		297.20	478.30	299	State Line, Idaho
		297.52	478.81		I-90 east	Continuation into Idaho
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus       Incomplete access

Reversible express lanes

The entire route is in King County.

Location	mi	km	Exit	Destinations	Notes
Seattle	1.99	3.20	—	Airport Way South, South Dearborn Street	HOV entrance and exit only
	2.21	3.56	—	Downtown Seattle Transit Tunnel	Bus only
	3.21	5.17	—	Rainier Freeway Station	Bus only
	3.66	5.89	—	I‑90 west to I‑5	Westbound off-ramp only (All Mercer Island SOVs exit here)
	3.87	6.23	—	I‑90 east	Eastbound on-ramp only (All Mercer Island SOVs enter here)
Mercer Island	6.58	10.59	7A	77th Avenue SE
	6.80	10.94	7B	Island Crest Way	All Mercer Island SOVs enter or exit here
	7.45	11.99	7C	80th Avenue SE	HOV entrance and exit only; this reversible ramp was converted to an HOV-only entrance onto the eastbound outer roadway in early 2012[51]
	8.01	12.89	—	I‑90 west	Westbound HOV entrance only
	8.39	13.50	—	I‑90 east	Eastbound HOV exit only
Bellevue	8.90	14.32	—	I‑405	Eastbound HOV entrance only
	9.44	15.19	9	Bellevue Way	HOV entrance and exit only
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Closed/former       HOV only       Incomplete access

References

1. "Route Log and Finder List - Interstate System: Table 1". FHWA. Retrieved August 5, 2007.
2. Washington State Department of Transportation, State Highway Log, 2006
3. Official State Highway Map (PDF) (Map) (2008–2009 ed.). 1:842,000. Official State Highway Maps. Cartography by U.S. Geological Survey. Olympia, Washington: Washington State Department of Transportation. 2008. Retrieved August 7, 2008.
4. Washington Large Print (Map) (2007 ed.). GM Johnson Large Print State Maps. Burnaby, British Columbia: GM Johnson. 2007. Retrieved August 8, 2008.
5. U.S. Route 2 Overview Map (Map). Cartography by NATVEQ. Google Maps. 2008.
6. U.S. Route 12 Overview Map (Map). Cartography by NATVEQ. Google Maps. 2008.
7. Google (July 31, 2008). "Interstate 82 Overview Map" (Map). Google Maps. Google. Retrieved July 31, 2008.
8. Google (July 31, 2008). "Interstate 90 Overview Map" (Map). Google Maps. Google. Retrieved July 31, 2008.
9. Washington State Department of Transportation (2007). "Washington Annual Average Daily Traffic Data" (PDF). Archived from the original (PDF) on March 26, 2009. Retrieved August 26, 2008.
10. Staff (2010-07-09). "National Register Information System". National Register of Historic Places. National Park Service.
11. Seattle Map Book (Map) (2006 ed.). City Street Maps. Burnaby, British Columbia: GM Johnson. 2006. Retrieved September 13, 2008.
12. United States Department of Transportation. "Preliminary List of Nationally and Exceptionally Significant Features of the Interstate Highway System". Retrieved September 20, 2008.
13. Bellevue, Redmond, Kirkland, Sammamish (Map) (2008 ed.). City Street Maps. Burnaby, British Columbia: GM Johnson. 2008. Retrieved September 13, 2008.
14. Washington State Department of Transportation. "WSDOT Interchange Viewer: Interstate 90 (Exit 2B to 22)". Retrieved September 13, 2008.
15. Map of I-90 (Seattle to Snoqualmie Pass) (Map). Cartography by NATVEQ. Google Maps. 2008.
16. The Road Atlas (Map). Rand McNally. 2008. p. 108. ISBN 0-528-93961-0.
17. The Road Atlas (Map). Rand McNally. 2008. p. 110. ISBN 0-528-93961-0.
18. Washington State Department of Transportation. "WSDOT Interchange Viewer: Interstate 90 (Exit 25 to 78)". Retrieved September 13, 2008.
19. Map of I-90 (Seattle-Bellevue Express Lanes) (Map). Cartography by NATVEQ. Google Maps. 2008.
20. WSDOT I-5 Express Lane Map (Map). Washington State Department of Transportation. 2006. Retrieved August 8, 2008.
21. Washington State Department of Transportation. "King County Express Lanes: Schedule". Retrieved January 31, 2009.
22. Go Northwest!. "Snoqualmie Pass in the Cascade Mountains of Washington". Retrieved August 24, 2008.
23. Map of I-90 (Snoqualmie Pass to Ritzville) (Map). Cartography by NATVEQ. Google Maps. 2008.
24. Washington State Department of Transportation. "WSDOT Interchange Viewer - Interstate 90 (Exit 80 to 149)". Retrieved September 13, 2008.
25. Washington State Department of Transportation. "WSDOT Interchange Viewer - Interstate 90 (Exit 151 to 215)". Retrieved September 13, 2008.
26. Map of I-90 (Ritzville to Idaho) (Map). Cartography by NATVEQ. Google Maps. 2008.
27. Spokane City Pearl (Map) (2005 ed.). Pearl City Maps. Burnaby, British Columbia: GM Johnson. 2005. Retrieved September 13, 2008.
28. Spokane (Map) (2007 ed.). City Street Map. Burnaby, British Columbia: GM Johnson. 2007. Retrieved September 13, 2008.
29. Inland Empire (Map) (2007 ed.). Burnaby, British Columbia: GM Johnson. 2007. Retrieved September 13, 2008.
30. Washington State Department of Transportation. "WSDOT Interchange Viewer - Interstate 90 (Exit 220 to 279)". Retrieved September 13, 2008.
31. Washington State Department of Transportation. "WSDOT Interchange Viewer - Interstate 90 (Exit 280 to 299)". Retrieved September 13, 2008.
32. Washington State Legislature (1913). "An act relating to public highways, classifying the same and naming and fixing the routes of certain state roads.". Session Laws of the State of Washington. Olympia, WA: State of Washington. 1913 chapter 65, p. 221.: "A highway starting from the Pacific Highway at Renton, Washington; thence over the most feasible route by the way of Snoqualmie Pass into the Yakima River Valley; thence by way of Wenatchee, over the most feasible route, through Waterville and Spokane, to the state boundary, which shall be known as the Sunset Highway."
33. Washington State Legislature (1913) [1913]. "65". Session Laws of the State of Washington. Session Laws of the State of Washington (1913 ed.). Olympia, Washington: Washington State Legislature. p. 221. Retrieved August 10, 2008.
34. State Highway Board, Road Map of Washington Showing Main Traveled Roads, 1912
35. State Highway Board, Map of Washington State Highways Authorized by Legislative Acts of 1913 (with 1915 changes marked)
36. Rand McNally, Official 1923 Auto Trails Map, District No. 14: Washington, Oregon, Northern California, Western Idaho
37. Washington State Legislature (1923). "An act relating to, classifying, naming and fixing the routes of certain state highways, amending Section 6796, and repealing Sections 6791, 6792, 6793, 6794, 6795, 6797, 6798, 6799, 6800, 6801, 6802, 6803, 6804, 6805, 6806, 6808, 6809, 6811, 6812, 6813 and 6816 of Remington's Compiled Statutes.". Session Laws of the State of Washington. Olympia, WA: State of Washington. 1923 chapter 185, p. 628.: "A primary state highway, to be known as State Road No. 2 or the Sunset Highway, is established as follows: Beginning at the City of Seattle; thence by the most feasible route in an easterly direction through the cities of Renton, North Bend, Cle Elum, Wenatchee, Waterville, Davenport and Spokane to the Washington-Idaho state line."
38. Washington State Legislature (1937). "An act relating to public highways, creating and establishing, describing and designating the primary state highways of the State of Washington and declaring an emergency.". Session Laws of the State of Washington. Olympia, WA: State of Washington. 1937 chapter 190, p. 941.: "A primary state highway to be known as Primary State Highway No. 18 is hereby established according to description as follows: Beginning at the wye junction on Primary State Highway No. 7, near Burke, thence in an easterly direction by the most feasible route by way of Neppel to a junction with Primary State Highway No. 11 at Ritzville."
39. Bureau of Public Roads & American Association of State Highway Officials (November 11, 1926). United States System of Highways Adopted for Uniform Marking by the American Association of State Highway Officials (Map). 1:7,000,000. Washington, DC: U.S. Geological Survey. OCLC 32889555. Retrieved November 7, 2013 – via University of North Texas Libraries.
40. Department of Highways, Highway Map: State of Washington, Revised to April 1, 1933
41. Department of Highways, Highways of the State of Washington (Rand McNally), 1939
42. Washington State Department of Transportation. "WSDOT - History of WSDOT (1921-1940)". Archived from the original on October 11, 2008. Retrieved August 11, 2008.
43. Washington State Department of Transportation. "WSDOT - History of WSDOT (1978-1990)". Archived from the original on August 30, 2008. Retrieved August 11, 2008.
44. Washington State Department of Transportation. "WSDOT - History of WSDOT (1991-2004)". Archived from the original on October 5, 2006. Retrieved August 11, 2008.
45. United States Department of Transportation/Federal Highway Administration (July 7, 2006). "The Greatest Decade 1956-1966 Part 1 Essential to the National Interest". Retrieved August 11, 2008.
46. United States Department of Transportation/Federal Highway Administration. "History of the Interstate Highway System". Retrieved August 11, 2008.
47. Washington State Department of Transportation. "WSDOT - History of WSDOT (1967-1977)". Archived from the original on October 5, 2006. Retrieved August 11, 2008.
48. Washington State Legislature. "RCW 47.17.140: State route No. 90 — Washington green highway". Retrieved August 10, 2008.
49. "Mountains To Sound Greenway (Washington)". Retrieved August 24, 2008.
50. Washington State Department of Transportation. "WSDOT - Construction Projects on Interstate 90". Retrieved August 11, 2008.
51. "Changes ahead for I-90 Express Lanes". Washington State Department of Transportation. January 18, 2012. Archived from the original on July 10, 2014. Retrieved January 2, 2015.

External links

Route map: Bing / Google

• Interstate 90 @ Interstate-Guide.com
• Western Terminus of Interstate 90 @ Interstate-Guide.com
• Highways of Washington State