List of Interstate Highways in Washington

[14] Early proposals for a national system of "superhighways" with limited access and grade separation emerged in the 1930s at the behest of the Bureau of Public Roads (BPR; now the FHWA) under the Roosevelt administration.[15][16] The first major expressway with limited access to be built in the state was the Alaskan Way Viaduct in Downtown Seattle, which was announced in 1947 and used federal grants authorized by the Federal-Aid Highway Act of 1944.[20][21] A second bill in 1951 authorized the construction of expressways to replace rural sections of US 99 and US 10 (the east–west trunk), particularly by bypassing small cities, and the program was expanded to cover 2,388 miles (3,843 km) by 1953.[33] Among the first Interstate projects in Washington to be built with funding from the Federal-Aid Highway Act of 1956 were bypasses of Fort Lewis and Olympia that had already been planned by the state government.[37] The state government made improvements to the expanding Interstate system in the 1960s and 1970s, building rest areas and scenic overlooks on the primary routes and introducing mileage-based exit numbers in 1973.[40] The new connector, numbered I-182, was approved in 1969 and fully opened in 1986 alongside the last Washington section of I-82; the highways were delayed by disagreements with local governments and spending cuts during the early 1980s recession.[46][47] The final section of the Interstate system in Washington, I-90 between Seattle and Bellevue, took over 30 years to plan and construct amid disagreements and litigation over its design and other mitigation.[55] A 2004 study commissioned by the state legislature determined that an outer beltway would not be feasible to construct due to its high costs as well as opposition from local residents and environmental groups.
Aerial view of a freeway interchange with flying ramps situated over a dense urban neighborhood.
Aerial image of the I-5 and I-90 interchange south of Downtown Seattle
Aerial view of a suburban neighborhood with a diagonal swath cleared of homes and turned into dirt. A few roads cross over the dirt trench.
Construction of I-5 in north Seattle, 1963
List of Interstate Highways in Washington, D.C.Highway markersInterstatesBusiness LoopsBusiness SpursState highways in WashingtonScenicPre-19641964 renumberingFormerInterstate Highway SystemWashingtonWashington State Department of Transportationdesign standardsFederal Highway AdministrationAmerican Association of State Highway and Transportation Officialsauxiliary routesInterstate 90SeattleSpokaneOregonstate lineCanadian borderbusiness routesU.S. CongressFederal-Aid Highway Act of 1956tollwayBellevueDowntown Seattlestate highway systemfreewaysInterstate Highway standardsgrade separationcontrol of accessinterchangesshouldersprimary routesU.S. routesstate routesreversible express lanesPortland–Vancouverhigh-occupancy vehiclestolled vehiclesvehicle miles traveledlimited accessBureau of Public RoadsRoosevelt administrationWest CoastNorthern statesexpresswayAlaskan Way ViaductFederal-Aid Highway Act of 1944U.S. Route 99United States Numbered Highway SystemWashington State LegislatureTacomaBritish ColumbiaUS 10bypassingPortland, OregonVancouver, WashingtonDwight D. EisenhowerEllensburgPendleton, OregonCascade RangeAberdeenFort LewisOlympiaInterstate shieldEverettMarysvilleWoodinvilleLynnwoodrest areasscenic overlooksexit numbersYakimaTri-Citiesspur routeearly 1980s recessionGlenn L. Jackson Memorial BridgeColumbia RiverHomer M. Hadley Memorial BridgeLacey V. Murrow Memorial Bridgefloating bridgesMount Baker TunnelMercer IslandbeltwayEastsideLake SammamishSR 18Snoqualmie ValleyVancouverHighway 99BlaineUS 97US 395PlymouthYakima ValleySR 519Liberty LakeMount RainierFred G. Redmon BridgeInterstate 90 floating bridgesLake WashingtonNorth BendVantage BridgeUS 12RichlandSalmon CreekSR 518TukwilaSR 525Downtown BellevueRevised Code of WashingtonThe Everett HeraldThe Seattle TimesSeattle Post-IntelligencerHistoryLinkThe Spokesman-ReviewNewspapers.comHoughton Mifflin HarcourtWikiSourcePublic Roads AdministrationPort Angeles Evening NewsAssociated PressThe New York TimesProQuestLibrary of CongressThe EnterpriseTri-City HeraldThe ColumbianThe OregonianMeasuringWorthGross Domestic Product deflatorSnoqualmie Valley RecordWayback Machine