Interstate 90 in Washington

Interstate 90 (I-90), designated as the American Veterans Memorial Highway, is a transcontinental Interstate Highway that runs from Seattle, Washington, to Boston, Massachusetts. It crosses Washington state from west to east, traveling from Seattle across the Cascade Mountains and into Eastern Washington, reaching the Idaho state line east of Spokane. I-90 intersects several of the state's other major highways, including I-5 in Seattle, I-82 and U.S. Route 97 (US 97) near Ellensburg, and US 395 and US 2 in Spokane.

I-90 is the only Interstate to cross the state from west to east, and the only one to connect the state's two largest cities, Seattle and Spokane. It 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. I-90 crosses the Cascades at Snoqualmie Pass, one of the busiest mountain pass highways in the United States, and uses a series of viaducts and structures to navigate the terrain. The freeway travels across suburban bedroom communities in the Seattle metropolitan area, the forests of the Cascade Range, and the high plains of the Columbia Plateau.

The crossing at Snoqualmie Pass was established as a wagon road in 1867 and incorporated into a cross-state auto trail, known as the Sunset Highway, in the early 1910s. The Sunset Highway was incorporated into the national highway system in 1926 as part of US 10, which I-90 replaced when it was designated in 1957. The first segments of the freeway, located in Spokane and Spokane Valley, opened at around the same time and the state government completed upgrades of US 10 to Interstate standards for most of the route by the late 1970s.

The section of I-90 between Seattle and I-405 in Bellevue was delayed for decades because of environmental concerns and lawsuits by local groups over the freeway's potential impact on nearby neighborhoods. A compromise agreement was reached by the federal, state, and local governments in 1976 to build a second floating bridge across Lake Washington and include extensive parks above tunneled sections of I-90, which were completed in the early 1990s. The new floating bridge opened in 1989 and carried bi-directional traffic while the original floating bridge was renovated. The old bridge's center pontoons sank during a November 1990 windstorm due to a contractor error and were rebuilt over the following three years, reopening to traffic on September 12, 1993, marking the completion of the transcontinental highway.

Route description

Interstate 90 is the longest freeway in Washington state, at nearly in length, and is the only Interstate to traverse the state from west to east across the Cascade Mountains., wit
inset maps
It is listed as part of the National Highway System, classifying important to the national economy, defense, and mobility, and the state's Highway of Statewide Significance program, recognizing its connection to major communities. The Washington State Legislature designated the highway as the "American Veterans Memorial Highway" in 1991 to honor U.S. soldiers. A section of I-90 between Seattle and Thorp named the Mountains to Sound Greenway was designated in 1998 as a National Scenic Byway, in recognition of its scenic views.

I-90 is maintained by the Washington State Department of Transportation (WSDOT), who conduct an annual survey of traffic volume that is expressed in terms of average annual daily traffic (AADT), a measure of traffic volume for any average day of the year. A section of I-90 in Bellevue's Eastgate neighborhood carries a daily average of 150,000 vehicles, making it the highway's busiest. The highway's least busiest section, near SR 21 west of Ritzville, carried 11,000 vehicles in 2016. The freeway has a maximum speed limit of in urban areas, in mountainous areas, and in rural areas. Several proposals to raise the speed limit of the rural section between Vantage and Spokane to have been submitted and denied by the state government due to safety concerns.

Seattle, Mercer Island, and Bellevue

I-90 begins its eastward journey at the intersection of Edgar Martinez Drive South (part of SR 519) and 4th Avenue South in the SoDo neighborhood south of Downtown Seattle. The interchange is adjacent to T-Mobile Park, home to the Seattle Mariners baseball team, and includes a pair of ramps to SR 519 and an additional offramp to 4th Avenue South north of Royal Brougham Way and near Lumen Field. The ramps converge over the Stadium light rail station adjacent to King County Metro's bus bases and were formerly joined by bus-only express lane ramps from the Downtown Seattle Transit Tunnel and 5th Avenue in the International District. I-90 travels east through a major interchange with I-5 at the northwest corner of Beacon Hill and passes under the Jose Rizal Bridge.

The freeway wraps around the north end of Beacon Hill and intersects Rainier Avenue at the site of the future Judkins Park light rail station, joined by a multi-use bicycle and pedestrian trail that forms part of the Mountains to Sound Greenway. I-90 travels east into the Mount Baker Tunnel, a set of tunnels which run under Sam Smith Park and the Mount Baker Ridge neighborhood to Lake Washington; they are also listed on the National Register of Historic Places. At the east end of the tunnels, traffic continues onto a pair of floating bridges; the eastbound lanes are carried by the Lacey V. Murrow Memorial Bridge, while the westbound lanes, multi-use trail, and future light rail tracks are carried by the wider Homer M. Hadley Memorial Bridge. The two floating bridges connect Seattle to the Eastside suburbs and are among the longest in the world, at and in length, respectively.

From the east end of the bridge, I-90 continues onto Mercer Island and travels under the Mercer Island Lid, a landscaped park built atop a curved section of the freeway between West Mercer Way and 76th Avenue Northeast. I-90 emerges in downtown Mercer Island, adjacent to its future light rail station in the freeway median and a current park and ride. The freeway passes under a smaller lid at Luther Burbank Park and leaves the island on the East Channel Bridge, which crosses a smaller arm of Lake Washington into Bellevue. I-90 travels to the south of Enatai and Beaux Arts Village and intersects Bellevue Way, where light rail tracks turn north away from the freeway, before crossing the Mercer Slough and its wetlands. After crossing under a disused railroad bridge, slated to be part of the Eastside Rail Corridor trail, I-90 and its short set of collector–distributor lanes meet I-405 in a large stack interchange northwest of the Factoria Mall and the headquarters of T-Mobile US. South of the Bellevue College campus in Eastgate, I-90 intersects 142nd Place Southeast using direct ramps from its high-occupancy vehicle (HOV) lanes. Near the former Bellevue Airfield, I-90 turns southeast to run downhill from Cougar Mountain and along the shore of Lake Sammamish towards Issaquah.

East King, Snoqualmie Pass, and Kittitas

At the south end of Lake Sammamish and northwest of downtown Issaquah, I-90 passes through Lake Sammamish State Park and intersects SR 900. The freeway travels along the north edge of downtown Issaquah, zig-zagging to the south and north to avoid the ridge of Issaquah Highlands and western Tiger Mountain. I-90 leaves Issaquah and enters the heavily forested Issaquah Alps, skirting the north edge of the Tiger Mountain State Forest as it passes Preston. Northeast of Tiger Mountain, the freeway intersects SR 18 and an arterial street connecting to Snoqualmie and Snoqualmie Ridge. I-90 continues southeast past the Snoqualmie Casino to North Bend, where it intersects SR 202. The freeway travels around the southern edge of North Bend and neighboring Tanner in the foothills of Rattlesnake Ridge. I-90 continues southeasterly along the South Fork of the Snoqualmie River into the Snoqualmie National Forest, which also hosts several state parks and campgrounds.

I-90 continues in a southern arc around several mountains in the Alpine Lakes Wilderness while following the South Fork of the Snoqualmie River. At the east end of the arc near the Asahel Curtis Picnic Area, the freeway's westbound and eastbound lanes are split by a wide median that includes the Denny Creek Campground. I-90 continues northeast on two high viaducts and ascends to Snoqualmie Pass, the lowest of the state's three major Cascades passes at an elevation of . The pass handles 28,000 vehicles (including 6,500 trucks) on an average weekday, making it one of the busiest mountain highways in the United States. I-90 intersects the Pacific Crest Trail and SR 906 at the pass, providing access to the adjacent Snoqualmie ski resort. The freeway travels south into Kittitas County and intersects SR 906 Spur at Hyak. I-90 continues south through the Wenatchee National Forest along the eastern shore of Keechelus Lake, under steep cliffs that were cut using controlled blasting. At the south end of the lake, the freeway passes under a arched wildlife bridge, which is the first to be built in Washington state.

While Snoqualmie Pass does not have an annual closure like other passes in the Cascades, it does suffer from vehicle restrictions and occasional days-long shutdowns during the wintertime for avalanche control and clearing collisions. I-90 has several chain-on and chain-off areas on the highway shoulders between North Bend and Cle Elum, including variable-message signage to inform drivers of road conditions. WSDOT estimates that it costs $2–3 million annually to keep Snoqualmie Pass open in the wintertime, which sees an average snowfall of and about 120 hours of closures per year.

I-90 continues southeast along the Yakima River to Easton, where it leaves the national forest and is joined by the Palouse to Cascades State Park Trail, part of Iron Horse State Park. The freeway passes several ranches and resort communities, including Suncadia, before reaching Cle Elum. I-90 runs to the south of downtown along the Yakima River and intersects SR 10 east of the city before crossing the river. SR 10 follows the former route of US 10 on the north side of the Yakima River, connecting to SR 903 and SR 970. The two highways continue southeast along the Yakima River and enter the Kittitas Valley near Thorp. I-90 begins a concurrency with US 97 west of Ellensburg, which continues as the freeway travels around the outskirts of the city to an interchange with I-82, which travels south with US 97 along the Yakima River towards Yakima.

Columbia Plateau and Spokane area

I-90 crosses into the Columbia Plateau at the east end of the Kittitas Valley, traveling due east past Olmstead Place State Park and the town of Kittitas. The freeway travels across a series of hills while following the Ryegrass Coulee, including a rest area at Ryegrass Hill near the Wild Horse Wind Farm. I-90 then reaches Vantage, where it travels past the Ginkgo Petrified Forest State Park, one of the largest collections of petrified trees in the world, before crossing the Columbia River on the Vantage Bridge. The bridge ascends up to the cliffs on the western shore of Grant County, where I-90 intersects SR 26 and turns north along the Babcock Bench. The freeway then passes several scenic viewpoints for Lake Wanapum and the Wild Horse Monument, a piece of public art placed atop a hill to the east.

Near Frenchman Coulee and the Gorge Amphitheater, I-90 turns northeast towards George, where it intersects SR 281 and SR 283, providing access to Quincy and Ephrata, respectively. The freeway continues due east across rural Grant County, paralleled by a pair of frontage roads, past several sand dunes, state recreational areas, and the Potholes Reservoir. I-90 reaches Moses Lake by crossing the eponymous lake's western arm and intersecting SR 171, which serves as the city's main street. The freeway then crosses the Pelican Horn and intersects SR 17 before leaving the city, regaining its frontage roads as it continues east across rural Adams County by following several coulees. I-90 intersects the SR 21 east of the Schrag rest area and continues towards Ritzville, where a long concurrency with US 395 begins. The two highways intersect SR 261 and travel northeast along the BNSF railroad, which carries Amtrak's '' Empire Builder'' trains, to Sprague Lake in Lincoln County. In Sprague, I-90 intersects SR 23 just south of its junction with SR 231. From Sprague, the freeway passes the Fishtrap Recreation Area and crosses into Spokane County, where it alternates between interchanges with SR 904 and SR 902, which form loops serving Medical Lake and Cheney, respectively.

I-90 and US 395 continue along the south side of Spokane International Airport and enter the city of Spokane, adding US 2 to the concurrency at an interchange near Sunset Hill. The three highways continue along Garden Springs Creek and the John A. Finch Arboretum to an interchange with US 195, located under several railroad overpasses. The freeway continues across Latah Creek into Downtown Spokane, where it travels on an elevated viaduct along 4th Avenue on the south side of downtown. The freeway passes the city's two hospitals ( Deaconess and Sacred Heart) before intersecting Browne and Division streets, which carry US 2 and US 395 north through Spokane. I-90 then intersects SR 290 at the eastern edge of downtown, providing a connection across the Spokane River to the Gonzaga University campus.

The freeway continues east through Spokane's suburban neighborhoods, flanked by a pair of frontage roads that funnel traffic towards local streets at interchanges, and passes the future terminus of the North Spokane Corridor, a major freeway that will carry US 395 when completed. I-90 then enters Spokane Valley near Avista Stadium and the Interstate Fairgrounds. The freeway travels on the north side of the suburban city and intersects SR 27 near the Spokane Valley Mall. I-90 follows the Spokane River and Centennial Trail through Liberty Lake and to the Idaho state line. The freeway then continues across the Spokane River towards Post Falls and Coeur d'Alene.

History

Early state roads

Snoqualmie Pass was historically used by the indigenous inhabitants of the Puget Sound and Columbia Plateau regions for trade and socializing in the summertime, as it was the lowest pass in the Cascades. The early trails from the pass were used by fur traders and settlers beginning in the 1850s, as it was the only route equipped to handle wagons and livestock. Snoqualmie Pass was later chosen for the region's first major cross-mountain road in the 1860s, having beaten the federal government's favored route over Naches Pass, and a rough wagon road was completed in October 1867 by a group of Seattle businessmen.

The wagon road was popular with settlers and cattle drivers from eastern Washington and was planned to be extended west to the Black River and east to the Yakima Valley using a $2,500 appropriation from the territorial government, but the funds proved insufficient and the project was shelved. The Snoqualmie wagon road was bought out in 1883 by the Seattle and Walla Walla Trail and Wagon Road Company and converted into a toll road to fund maintenance after the federal government declined to fund improvements to the road. The toll scheme was ultimately unsuccessful, as it failed to compete with the Northern Pacific Railway after it built its railroad across Stampede Pass to the south. The toll road was abandoned in 1893 and transferred to King and Klickitat counties, who contracted Denny to maintain and repair the road in 1899 with state money; by that time, sections of the road had deteriorated considerably, but approximately 200 wagons and 1,148 used the Snoqualmie Pass road that summer.

The rise of automobiles after the turn of the 20th century led to the state government funding and supporting new highways across Washington state. Snoqualmie Pass saw its first automobile crossing in 1905, the same year that the state government designated the route as part of State Road 7. State Road 7 began construction between North Bend and Easton in 1907 and became Washington's first trans-Cascades highway. Later that year, state highway commissioner Joseph M. Snow announced plans to extend the Snoqualmie Pass road west to Seattle and east to Spokane and the Idaho state line, using a road through Wenatchee. The cross-state extension was approved by the state legislature in 1909 and commemorated by a 23-day automobile race from New York City to Seattle for that year's Alaska–Yukon–Pacific Exposition; in total, 105 automobiles crossed Snoqualmie Pass in 1909. The racers and a group of Spokane motorists who drove across two years later described the road near Snoqualmie Pass as "impassible" with "treacherous" conditions, leaving much to be improved.

Sunset Highway and national routes

In 1912, the state good roads association endorsed the construction of three trunk highways across the state, including a route from the Puget Sound to Idaho over Snoqualmie Pass. The state legislature passed an appropriations bill in March 1913 that funded construction of the trunk routes, including a total of $506,834 for the cross-state road, dubbed the " Sunset Highway". Construction of the Sunset Highway through Snoqualmie Pass began in February 1914, with the goal of lowering the crossing of the pass by under the old wagon road. To extend the highway from Ellensburg to Spokane, the state highway board chose to route the Sunset Highway over a ferry crossing of the Columbia River at Vantage, then north to Wenatchee and Waterville along modern US 2. In Spokane, the Sunset Highway met the Central Washington Highway (State Road 11), which ran southwest through Cheney and Ritzville towards the Tri-Cities. The road across Snoqualmie Pass was mostly complete by September 1914, leading to plans for a formal dedication, but heavy rainfall delayed earthwork along the highway and postponed its use by motorists.

The completed Sunset Highway was briefly opened for traffic on October 1, 1914, before closing for the winter season. It reopened to traffic on June 20, 1915, and the highway was formally dedicated at the summit of Snoqualmie Pass on July 1, 1915, by a party of 400 motorists led by Governor Ernest Lister and Seattle Mayor Hiram Gill. Lister compared the highway's opening to the arrival of the transcontinental railroads and called the completion of the Sunset Highway the more important achievement for the state. In 1919, the state government rerouted the Sunset Highway between Ellensburg and Wenatchee, proposing a new branch through Blewett Pass in lieu of the ferry crossing at Vantage, which became part of the North Central Highway. The Blewett Pass highway was completed in May 1922, replacing a more dangerous wagon road across the pass. Portions of the Sunset Highway remained graded but unpaved until funds from the Federal Aid Road Act of 1916 were used to pave a gravel surface; some sections in King County were also upgraded with concrete pavement.

The Sunset Highway was renumbered to State Road 2, as part of a statewide reorganization of the highway system in 1923; the Vantage segment was retained as part of North Central Highway, renumbered as State Road 7, and the Ritzville–Spokane highway became part of State Road 11. The Sunset Highway became part of two transcontinental auto trails in the late 1920s: the National Park to Park Highway and the Yellowstone Trail, which was rerouted away from the Inland Empire Highway in 1925. The federal government established its own national highway system in 1926, designating the Sunset Highway as part of U.S. Route 10 (US 10), a transcontinental highway between Seattle and Detroit, Michigan. At the time, the Sunset Highway had with gravel paving, with cement pavement, with macadam, with bricks, and with asphalt concrete; only of the highway remained without any sort of pavement beyond graded dirt.

The state highway department continued work near the Snoqualmie and Blewett passes, including the staging of snow removal vehicles to allow for all-winter travel beginning in 1930–31 and a segment near Snoqualmie Pass being completely paved in 1933. The year-round access to Snoqualmie Pass led to a rise in local skiing, especially at the ski area operated by the Seattle city government. By the end of the decade, the entire Sunset Highway was paved with either asphalt or concrete. The state highway system was restructured once again in 1937, leading to the creation of primary and secondary highway designations. State Road 2 became Primary State Highway 2 (PSH 2), still retaining its concurrency with US 10; similar carryovers followed for State Road 7 and State Road 11, which became PSH 7 and PSH 11, respectively. A new highway, PSH 18, was created and ran from PSH 7 at Burke near Quincy and through Moses Lake to PSH 11 and US 395 in Ritzville. US 10 was rerouted onto the new Burke–Ritzville highway and a section of PSH 7 between Thorp and Burke, incorporating the original Vantage Bridge, in the early 1940s. The old alignment through Wenatchee, Coulee City, and Davenport, along with a new segment across Stevens Pass to Everett, was designated as US 10 Alternate in the early 1940s. US 10 Alternate itself was usurped by the extension of US 2 from Sandpoint, Idaho, to Everett in 1946.

A second alternate route was established in the 1940s after the opening of the Lake Washington Floating Bridge between Seattle and Mercer Island. US 10 previously traveled between Seattle and Issaquah via the south side of the lake, passing through Renton and crossing the Issaquah Alps. The terminus of US 10 remained at the intersection of Airport Way and 4th Avenue South (carrying US 99) between King Street and Union stations, the city's main railroad terminals. The floating bridge was conceived by engineers in the 1930s as a replacement for the automobile ferries on the lake and was opened on July 2, 1940, after one year of construction. The bridge, which initially had a toll of 25 cents, reduced the drive to the pass by and encouraged new suburban development on the Eastside that grew in the following decades. A new section of US 10 between Issaquah and North Bend was also constructed the following year, bypassing the towns of Fall City and Snoqualmie. Upgrades to the Snoqualmie Pass section of the highway began in 1950, expanding the road to four lanes and constructing two snowshed