Pacific Highway and U.S. Route 99 SR 99 was created from the remnants of US 99, a national highway which spanned
Western Washington from the Oregon border in
Vancouver to the
Canadian border at the
Peace Arch in
Blaine. US 99 itself was preceded by a century-old network of
military roads, wagon roads, and auto trails that were built across the state in the 19th century and early 20th century until it was formally incorporated into the state highway system. In southern King County, modern-day SR 99 runs parallel to a section of the
Fort Steilacoom–
Fort Bellingham military road, constructed in the 1850s by the U.S. Army. A section north of Seattle follows the R.F. Morrow wagon road, constructed in 1901 and later incorporated into the North Trunk Road. The North Trunk Road was completed from Seattle to the area east of Edmonds in August 1912 and initially paved with bricks. The
Seattle–Everett Interurban Railway was also built along sections of the wagon road in 1906 and would serve Everett–Seattle traffic until 1939. The
Pacific Highway, an inter-state coastal highway, was championed by
good roads advocates in the early 1910s and added to the state highway system in 1913. It originally followed the
Puyallup and
Green rivers from
Tacoma to
Renton and the Bothell–Everett Highway (now SR 527) along North Creek in Snohomish County. The highway was designated as State Road 1 in 1923, a number that it would retain after the creation of
Primary State Highway 1 (PSH 1) in 1937. The Pacific Highway was incorporated into the new
national numbered highway system in 1926 as US 99, connecting the three West Coast states and running from the
Mexican border to Canada. The Bothell route was bypassed by a newer and straighter highway to the west that opened on October 9, 1927, shortening the distance from Seattle to Everett by and featuring overpasses for the existing interurban and a gravel
median strip in some sections. It was built by the state government in tandem with a set of new bridges connecting Everett to
Marysville and cost $645,000 (equivalent to $ in dollars) to construct and partially pave. The White River route was bypassed in early 1928 by the Highline route, which traveled along the western plateau near
Des Moines. The new highway cost $3 million (equivalent to $ in dollars) to construct and pave and reduced the distance to Tacoma by . US 99 was originally routed north from Downtown Seattle on 4th Avenue,
Westlake Avenue, 7th Avenue, and Dexter Avenue, crossing the Lake Washington Ship Canal on the
Fremont Bridge before continuing onto Fremont Avenue. A high-level crossing of the Ship Canal to replace the existing drawbridges was proposed in the 1920s as the "final link" in the Pacific Highway. The bridge was funded by the state, county, and municipal governments and approved for construction in 1927. Construction on the bridge began in 1929 and was completed on February 22, 1932, during a dedication ceremony that named it the
George Washington Memorial Bridge. The bridge was sited on Aurora Avenue, which was expanded into a
limited-access expressway that extended south to Denny Way and north through Woodland Park to North 65th Street. The expressway on the north side of the bridge was completed in May 1933 after a public debate over its routing through Woodland Park, which was opposed by
The Seattle Times and conservationists. The debate was settled after the passing of a
city council ordinance in June 1930 and a ballot measure in November that approved the through-park route.
Viaduct and expressway construction Within Downtown Seattle, US 99 was routed along 4th Avenue, connecting to the north with the Aurora Avenue expressway via 7th Avenue and to the south with East Marginal Way near Boeing Field. An
alternate route was designated in the early 1950s along 1st Avenue, rejoining the highway in
Georgetown. The bypass viaduct gained popularity following the end of
World War II and engineering work was approved in 1947, with construction funds sourced from the city and the
Federal-Aid Highway Act of 1944. A double-deck elevated design was chosen to accommodate the six lanes that would displace railroads along the east side of Alaskan Way. Construction on the Alaskan Way Viaduct began on February 6, 1950, and the first section between Railroad Way and Elliott Avenue opened to traffic on April 4, 1953. It cost approximately $8 million to construct (equivalent to $ in dollars), using pile-driven columns and a pair of moving
gantry cranes to lift sections of the roadway from street level. The Battery Street Tunnel, connecting the viaduct with the Aurora Avenue expressway, was opened to traffic on July 24, 1954, and cost $2.8 million to construct (equivalent to $ in dollars). A extension of the viaduct, linking south to a surface freeway and US 99 at East Marginal Way, cost $7.6 million to construct (equivalent to $ in dollars) and opened on September 3, 1959. The southern extension eased congestion at the Railroad Way terminus and was used by a daily average of 25,000 vehicles within days of opening and 37,000 vehicles by the end of the year. A series of ramps connecting the viaduct to the Spokane Street Viaduct were completed in January 1960, followed by a downtown offramp to Seneca Street in November 1961 and onramp from Columbia Street in February 1966. The state government had prepared to build a set of ramps from the viaduct to
US 10 (later part of
I-90) near Connecticut Street, but plans for the freeway were delayed in the 1960s and eventually abandoned, leaving the ramps
unused. The viaduct was initially signed as part of U.S. Route 99 Alternate and US 99 Bypass until 1959, when US 99 was formally switched to the viaduct after the completion of the southern extension. 4th Avenue was signed as a
business route of US 99 and also carried a section of US 10 to its terminus at the north end of the Battery Street Tunnel. The East Marginal Way route through the Boeing Field area was heavily congested due to traffic heading to Boeing facilities, leading to proposals in the 1950s to build a new expressway on the west side of the Duwamish River. Construction of the
two-lane West Marginal Way expressway began in November 1958 and was completed in July 1959, including grade-separated interchanges and bridges at South 118th Street, 14th Avenue South, and South Cloverdale Street. The expressway split from US 99 at South 118th Street and connected to 1st Avenue at the south end of the viaduct using the First Avenue South Bridge, which opened in 1956 with the intent of becoming part of US 99. In March 1959, the state government approved $3 million in funds (equivalent to $ in dollars) for an expansion project that would widen the West Marginal Way expressway to four lanes. The expansion was completed in 1968, and was signed as US 99 Temporary and later State Route 99T after the
1964 state highway renumbering.
Replacement and redesignation until its removal in 2019|alt=A set of green highway signs reading "Southbound US 99" and "Waterfront" seen above a street intersection. The state legislature authorized planning of a
tolled expressway from Tacoma to Everett in 1953, with the intent of building a grade-separated bypass of US 99. The tollway plan was superseded three years later by the
Interstate Highway Program, which was authorized by the federal government and included a north–south freeway through the Seattle area replacing US 99. The route was designated as Interstate 5 in 1957 and planning for the Seattle Freeway began at the same time using federal funds. The first section of the Tacoma–Seattle–Everett freeway to be built was in southern Tacoma and was opened to traffic in October 1959. The Tacoma sections opened in October 1962 from the Puyallup River to the Kent–Des Moines Road (now SR 516) in Midway, and in October 1964 in downtown Tacoma. Construction of the Seattle section began in 1958 with work on the
Ship Canal Bridge, which was opened to traffic on December 18, 1962. The northern approach to Downtown Seattle was opened the following August to coincide with the completion of the
Evergreen Point Floating Bridge and
SR 520. A section of the freeway traveling from North Seattle to southern Snohomish County and Everett was opened to traffic on February 3, 1965. The freeway connecting Midway to the south side of Downtown Seattle was opened on January 31, 1967, completing the final section of the urban freeway. I-5 itself was completed two years later with the opening of the section between Everett and Marysville on May 14, 1969. The state government introduced a new highway numbering system in 1964 to align with the Interstates and prepare for the decommissioning of U.S. routes. PSH 1 was replaced with US 99, which remained as a temporary designation on various freeway sections until I-5 was fully completed. US 99 was decommissioned at a meeting of the
American Association of State Highway Officials on June 24, 1969, shortly after the full completion of I-5 within Washington state. While most US 99 signs were removed, an overhead sign in Downtown Seattle at the Columbia Street onramp to the Alaskan Way Viaduct remained until the viaduct was demolished in 2019. During the 1970 codification of the new highway system, the state legislature created State Route 99 (SR 99) to delay transferring ownership and maintenance of the highway to local jurisdictions. SR 99 was created from a section of US 99 that ran from Fife to the Broadway Interchange in Everett, A provision in the 1971 law allows for the abandonment of the Fife–Federal Way section of SR 99 after the completion of the SR 509 freeway extension.
Street and bridge improvements , formerly part of SR 99 until a jurisdictional transfer in 2004|alt=An aerial view of a suburban street with several traffic lanes and traffic lights amid strip malls and gas stations. Sections of SR 99 in North Seattle along Aurora Avenue and in South King County declined economically after the opening of Interstate 5, losing businesses amid increased crime. It became a notorious haven for drug dealers, prostitutes, the homeless, and strip clubs by the 1970s and 1980s. The stretch from Federal Way to Tukwila in South King County, popularly known as the "SeaTac Strip", was where the Green River Killer (
Gary Ridgway) picked up many of his victims in the 1980s. The highway was also unsafe for pedestrians and cross-traffic due to the lack of crossings and improper management of utility lines and overgrown foliage. In southern King County, the cities of Federal Way, SeaTac, and Tukwila drew up redevelopment plans that were largely built out in the 2000s, reducing traffic collisions and crime while improving the area's appearance. The city of Shoreline was incorporated in 1995 and made the redevelopment of Aurora Avenue into an early priority, completing its $140 million modernization and
multi-use trail project in stages between 2008 and 2017. The project included new traffic signals, BAT lanes, underground utility lines, and two pedestrian bridges. Edmonds plans to add widened sidewalks with planted buffer zones, new crosswalks, and turn lane pockets to its section of SR 99 beginning in 2022. The city of Seattle also plans to improve its section of Aurora Avenue North, but funding shortages and the timing of WSDOT repaving projects have led to a lack of sidewalks along some sections of the street. The Move Ahead Washington package, passed in 2022, includes $50 million in funds to rebuild sections of Aurora Avenue to include sidewalks, bicycle lanes, and landscaping. The Aurora Bridge, part of the expressway linking Aurora Avenue to downtown Seattle, was the site of frequent suicide jumps until a set of
emergency phones and new fences were installed in 2011 at a cost of $4.6 million to deter would-be jumpers. The bridge and its
expansion joints underwent a major
seismic retrofit that was completed in 2012 at a cost of $5.7 million; the retrofit was followed by a repainting and repaving project that was completed in two stages between 2016 and 2018 at a cost of $35 million. On September 24, 2015, a collision between an amphibious
Duck tour vehicle and a
charter bus on the Aurora Bridge killed four people and injured 50 more. The incident raised questions regarding the safety of Aurora Bridge, which lacks a median barrier and is the narrowest six-lane bridge in the state, with a lane width of . Other sections of Aurora Avenue were retrofitted to install median barriers in 1973, and the state government considered a 2003 plan to put barriers on the bridge and relocate the sidewalks to compensate for the additional weight but ultimately deferred any improvements. A similar double-decker freeway, the
Cypress Street Viaduct in
Oakland, California, collapsed during the
Loma Prieta earthquake in 1989 and killed 42 people, leading to intensified calls to replace the viaduct due to the realized earthquake risk. A 1995 study commissioned by the state government after the
Kobe earthquake found vulnerabilities in the Alaskan Way Viaduct's design that could cause severe damage and collapse during a major earthquake, along with
liquefaction risks due to the underlying
reclaimed land that the highway was built on. The study estimated that it would cost $118 million (equivalent to $ in dollars) to demolish the viaduct, $344 million (equivalent to $ in dollars) to retrofit the structure for earthquake resistance, and $530 million (equivalent to $ in dollars) to build a new elevated freeway to replace it; other options included replacing the freeway with a tunnel or a surface boulevard with
public transit on Alaskan Way, similar to
San Francisco's
Embarcadero. On February 28, 2001, the
Nisqually earthquake struck the Seattle area with strong shaking that caused signs of visible damage on the Alaskan Way Viaduct. The freeway was shut down for inspections, which found small cracks and other minor damage to non-structural elements that allowed it to reopen within 26 hours. Four more closures were ordered later in March and April due to pieces of concrete dropping onto the streets below, requiring emergency repairs to add steel rods to reinforce the columns. The first repairs were completed in November at a cost of $1.8 million and a set of new vehicle weight restrictions were implemented; in total, $14.5 million was spent on various repairs due to earthquake damage. Annual inspections and continued monitoring found that the earthquake had caused settling of up to into the soil and weakened connections between the columns and highway decks. Additional investigations also found unrelated damage to the underlying
seawall, which would need to be rebuilt to prevent a resulting collapse of the viaduct. An ongoing state study investigating a viaduct replacement strategy was accelerated by the state legislature using $5 million in funds, while a separate engineering study suggested immediate demolition of the structure due to a 1-in-20 chance of collapse in an earthquake within the next decade. In late 2001, WSDOT began work on an
environmental impact statement (EIS) for the viaduct replacement project using emergency funds from the state legislature and consulted the city government and community leaders to generate concepts. By the following year, a set of 76 concepts organized into four general alternatives were presented for public feedback. Among the options were an elevated freeway similar to the current viaduct and several tunnel concepts, including a
bored tunnel, a two-level
cut-and-cover tunnel, and a mined tunnel carrying one direction of traffic. Five finalist options were paired with the seawall replacement and evaluated in June 2002, with costs ranging from $3.5 billion for a rebuilt viaduct to $8.8–$11.6 billion for various tunnel designs.
Tunnel concept, advisory votes, and subprojects , pictured in 2015|alt=An open trench with a temporary steel bridge separates a boardwalk business from a parking lot. The tunnel plan was endorsed by WSDOT and the city council based on public support for waterfront revitalization, but design changes would be needed to bring down its cost. After voters rejected a statewide
gas tax referendum that would have funded a portion of the project's cost, WSDOT and the city government drafted new cost-saving concepts for a shorter tunnel and a surface boulevard that were included in the five options evaluated by the draft EIS in 2004. The six-lane, $4 billion tunnel option was chosen as the preferred alternative by WSDOT in late 2004, despite backlash from activists groups who favored a rebuilt viaduct or a waterfront boulevard. The state legislature passed an $8.5 billion
gas tax program in 2005, allocating $2 billion in funding for the viaduct replacement. A supplemental EIS was prepared in 2006 to include new project requirements for the Battery Street Tunnel area and evaluate the cut-and-cover tunnel and elevated options. Both options were rejected by voters, with 70 percent opposed to the tunnel and 55 percent opposed to the elevated concept. The governments of Washington state, King County, and Seattle agreed to re-evaluate the planning process for the viaduct replacement and split the main proposals from essential safety and traffic improvements that would be included in all alternatives. Although the column strengthening project was declared successful, further inspections found that the Columbia Street onramp had sunk an additional during the nearby construction. The southernmost stretch of the viaduct, between Holgate and King streets, was demolished in October 2011 and replaced with a six-lane elevated freeway that opened the following year at a cost of $115 million. Seattle voters approved a
bond measure in 2012 to replace the
Alaskan Way Seawall; the project began construction in 2013 and was completed in 2017 at a cost of $410 million, running 21 percent overbudget.
Deep-bored tunnel approved and contested The state government announced a new timeline for the project in January 2008, with Governor Gregoire declaring her intention to demolish the viaduct by 2012 regardless of Seattle's approval. Eight new concepts for a four-lane replacement were developed by June from a set of priorities developed for SR 99, I-5, and public transit in downtown. The eight options included two surface boulevards with transit improvements, a
one-way couplet, a set of two elevated freeways, an elevated freeway with a rooftop park, and three tunnels: a cut-and-cover tunnel, a lidded trench, and a deep-bored tunnel. Several early concepts, including a bridge across
Elliott Bay and a complete rebuild of the double-decked viaduct, were rejected by the panel of public officials. The final decision was delayed until after the
gubernatorial election, but would have to meet an end-of-year deadline imposed by the state legislature. In December 2008, two finalists were chosen for further study and consideration by the state legislature: a $2.3 billion elevated freeway and the $2.2 billion surface-transit option. While the deep-bored tunnel was not chosen as one of the two finalists, it remained popular with tunnel activists and was considered separately due to its $4.25 billion cost (equivalent to $ in dollars). On January 13, 2009, Governor Gregoire signed an agreement with Mayor Nickels and King County Executive
Ron Sims to ratify the deep-bored tunnel as the replacement for the Alaskan Way Viaduct, to be completed by 2015. $2.8 billion would be covered by state gas taxes and federal funds, leaving a $1.4 billion shortfall to be filled by the local government and potential
tolls. The state legislature passed a bill in April 2009 to commit $2.8 billion in state funding for the tunnel project, which Governor Gregoire signed the following month. In total, more than 90 alternatives were considered before the final agreement was reached in 2009. The tunnel project received $300 million in funds from the Port of Seattle in exchange for design input on the surface boulevard that would replace Alaskan Way. The city council approved a non-binding resolution to authorize the tunnel project, pending the outcome of
contract bidding, which was completed in December 2010 with the selection of Seattle Tunnel Partners (STP), a consortium led by
Dragados USA. STP presented a $1.09 billion plan to use a
tunnel boring machine, the world's widest, to complete the tunnel by late 2015. WSDOT signed the tunnel construction contract in January 2011, sending a set of contractor agreements to the city council for approval. The state's agreements were approved by the city council in February 2011, shortly before being symbolically
vetoed by Mayor McGinn; the veto was overridden by the end of the month—the 10th anniversary of the Nisqually earthquake—with an 8–1 city council majority. McGinn joined other tunnel opposition groups to file a referendum questioning whether the city council had the authority to approve the state and federal agreements. The referendum was initially blocked by a lawsuit filed by the city, but was approved and placed on the August 2011 ballot by a county judge. The referendum was approved by 58 percent of voters on August 16, 2011, authorizing the city's agreements with WSDOT. The
Federal Highway Administration completed its analysis of the project's final EIS and issued its record of decision with WSDOT later that month, allowing pre-construction activities to begin.
Tunnel boring and viaduct closure the tunnel boring machine and the unfinished interior of the SR 99 tunnel, seen in January 2017|alt=The inside of a large concrete cylinder with steel cables and forms on the sides. Ahead is a massive structure with several floors of machinery and a large yellow tube at the top. After the demolition of the viaduct's southernmost stretch and its lanes were realigned onto an adjacent bypass in 2012, crews began excavation of a launch pit to house the tunnel boring machine. Local officials, with the notable absence of Mayor Mike McGinn, participated in a ceremonial
groundbreaking was held for the tunnel on June 20, 2012. The tunnel boring machine was manufactured by
Hitachi Zosen in
Osaka, Japan, and named "
Bertha" in honor of Mayor
Bertha Knight Landes. Bertha arrived in Seattle on April 2, 2013, and its 40 pieces were assembled in the launch pit before tunnel boring began on July 30—setting a record for the world's largest tunnel boring machine. Tunnel boring was halted at near South Main Street in December 2013 after the machine encountered an unknown object that caused it to overheat. The object was found to be a steel pipe and
well casing that was left behind by a
groundwater research crew for the project in 2002. The pipe caused extensive damage to Bertha's cutterhead and main bearing seal, requiring the excavation of a rescue pit for repairs. Bertha reached the completed excavation pit in March 2015 and the machine's front end was disassembled and lifted to the surface to repair the damage, which was found to be more extensive than previously thought. The repaired cutterhead was lowered into the access pit in August 2015 and tunnel boring resumed on December 22, 2015, reaching past the pit the following month. During the two-year halt in tunnel boring, public officials considered alternative plans to accelerate demolition of the viaduct while awaiting tunnel completion. The project was named one of the worst
boondoggles in the United States by several transportation groups and critics, due in part to the stoppage and its high cost. Tunnel boring was halted by Governor
Jay Inslee in January 2016 due to the appearance of a sinkhole in Pioneer Square, but resumed the following month. The machine passed under the Alaskan Way Viaduct in April 2016, requiring a closure while the structure was monitored for movement, and reached the halfway mark in October. Bertha completed its bore on April 4, 2017, arriving at the north portal near Aurora Avenue for disassembly, which was completed in August. The tunnel portals and their maintenance areas were completed while work on the double-decker freeway inside the tunnel progressed behind the machine. The Alaskan Way Viaduct permanently closed on January 11, 2019, beginning a three-week realignment of ramps at the portals as ramps were prepared for the opening of the tolled
downtown tunnel on February 4, 2019. The remaining section of the viaduct was demolished in stages between February and November 2019, with some of the of rubble deposited into the Battery Street Tunnel as it was filled and sealed. A three-block section of Aurora Avenue between Denny Way and the new tunnel portal was raised and reconnected to cross-streets in 2019. The Alaskan Way promenade and boulevard project was completed in 2025 and cost $800million to construct using a ix of city, state, and private contributions. It spans and includes prominent pedestrian features, such as the
Overlook Walk near Pike Place Market, as well as bicycle lanes. The rebuilt section of Alaskan Way is four lanes wide for most of its length but expands to eight lanes near
Colman Dock to accommodate ferry queueing and bus lanes. The viaduct replacement megaproject is estimated to cost $3.3 billion, with $200 million of construction costs and additional funds for ongoing maintenance to be raised through tunnel tolls that began to be collected on November 9, 2019.
Future projects In 2022, community activists from the South Park neighborhood proposed removing a freeway section of SR 99 between SR 599 and SR 509 to improve local air quality. A federal grant was announced the following year to study the impact of a possible removal or redesign of the highway through South Park. ==Names and designations==