Early state and national highways The
Pacific Highway was formed in 1913 by the state government as the north–south trunk in its first highway system, following the general route of modern-day I-5. The trunk route, one of three suggested by
good roads activists for several years and studied by the state legislature in 1909, strung together several
wagon trails dating back as early as the 1840s, when settlers arrived in the
Puget Sound region from the
Willamette Valley via the
Cowlitz Trail. Part of the highway also followed the
military road constructed in the 1850s from
Fort Vancouver to
Fort Bellingham. The Washington section was part of a longer highway along the West Coast from Canada to Mexico, which was conceived by the Pacific Highway Association of North America in 1910. The Pacific Highway was dedicated by 60,000 people at the Peace Arch in Blaine on September 4, 1923, with a few sections still under construction. The federal government and the
American Association of State Highway Officials established a
national highway system in 1926, designating most of the Pacific Highway north of
Los Angeles as part of
U.S. Route 99 (US 99). The highway's Washington segment would ultimately be completed four years later with the opening of several bridges between Everett and Marysville. State Road 1 was re-designated in 1937 as
Primary State Highway 1 under the state's new highway numbering system, but was not signed as such, giving priority to the overlapping US 99. By 1941, the Pacific Highway was the busiest road in the Pacific Northwest and had been widened to four lanes in most urban areas because of traffic congestion, necessitating studies into by-passing cities along the corridor.
State upgrades and Interstate planning The federal government began planning for a national "superhighway" system in the late 1930s, including the US 99 corridor as the main route along the West Coast. The highway system, designed with a minimum of four lanes in rural areas and strict
grade separation, was approved for limited funding by Congress in 1944 and planned by the
Bureau of Public Roads over the following years. The US 99 corridor was included in the initial system announced three years later by the
Public Roads Administration. The state legislature adopted its own set of standards for
limited-access highways in 1947, later amending them to encourage upgrades to existing two-lane roadways. In 1951, the legislature authorized a $66.7 million
bond issue (equivalent to $ in dollars) to fund upgrades to US 99, including four-lane sections on all but of the highway and a modern "
freeway" through Vancouver. The plan was opposed by Governor
Arthur B. Langlie, who questioned its constitutionality on the basis that it could violate the state constitution's 18th amendment. The bond's use of future
gas tax revenues to pay interest would, under some interpretations, violate the amendment's requirement that the gas tax must be used for highway purposes, using it instead to pay off debts. Later that year, the
state supreme court upheld the legislature's authorization and allowed the program to move forward. A separate bill in 1953 authorized planning for a
toll highway between Tacoma and Everett to replace the nearly-complete
Alaskan Way Viaduct and other urban streets with grade crossings and 19 total interchanges. The upgrade program was divided into of four-lane highway and of two-lane highway in rural sections between Marysville and Blaine. Construction on the rural sections in southwestern Washington began in late 1951 and the first section near Kalama was opened early the following year. Major bypasses of Centralia, Fort Lewis, Kelso, Marysville, and Tumwater were completed in 1954. The Vancouver freeway opened on April 1, 1955, constituting the state's first grade-separated freeway and costing $7 million (equivalent to $ in dollars) to construct. In December 1955, the section between Chehalis and Olympia was moved onto a straighter highway that bypassed
Tenino and other small towns along the meandering route of the Pacific Highway. Its opening marked the end of the southern section of the upgraded US 99. The northern section was declared complete after a bypass of Mount Vernon and Burlington, including a
new bridge over the
Skagit River, was opened to traffic in June 1957. The
Federal-Aid Highway Act of 1956, signed into law by President
Dwight D. Eisenhower on June 29, 1956, formally authorized the creation and majority-federal funding of the
Interstate Highway System. The entire US 99 corridor was subsequently assigned the designation of "Interstate 5" in 1957 and the federal government allocated planning funds to begin engineering of the Seattle Freeway, which commanded its own Highway Department division.
Suburban and rural construction and opened in 1960 Washington was the fastest of the three West Coast states to upgrade sections of US 99 to four lanes and partial
Interstate standards using new interchanges, with only of the highway in northern Whatcom County still two-laned by 1959. Among the first projects to use federal funding from the 1956 act was an upgrade of the Fort Lewis highway to four-lane freeway standards, which opened in September 1957 and included the relocation of the military base's main gate to a new
cloverleaf interchange. Another early Interstate project, the Olympia Freeway, was opened to traffic on December 12, 1958, at a cost of $11.6 million (equivalent to $ in dollars). It also included a freeway section of US 101 and US 410 that intersected I-5 in the state's first three-level interchange. A rural section of freeway between Marysville and Mount Vernon was completed in early 1959. The first section of the Tacoma–Seattle–Everett freeway was opened to traffic on October 1, 1959, extending the Fort Lewis freeway from
Gravelly Lake near
McChord Field to South 72nd Street in southern Tacoma. The $4.68 million project (equivalent to $ in dollars) built the six-lane freeway and a cloverleaf interchange at
SSH 5G (now SR 512). The Tacoma section was also the first to use the
Interstate highway shield, which was installed during construction in 1958. By the end of 1959, new interchanges and overpasses had brought most of the highway between Vancouver and Olympia to Interstate standards. Governor
Albert D. Rosellini announced an accelerated push for freeway construction, primarily aimed at completing Interstate 5 between Seattle and the Canadian border, in August 1960. The Tacoma section was extended north to
Midway (near Des Moines) on October 10, 1962. The dedication ceremony was attended by Governor Rosellini and included a parade of
U.S. Army vehicles from
Fort Lewis. The Tacoma–Midway section cost $14.5 million to construct (equivalent to $ in dollars) and included a cloverleaf interchange for the Auburn cutoff (later SR 18) in Federal Way. The ceremony had been preceded by drivers trespassing onto the finished but unopened freeway a month earlier to avoid congestion on US 99. The Tacoma and Olympia sections of I-5 were connected by a new freeway across Fort Lewis and the Nisqually River that opened in November 1968 and cost $12 million (equivalent to $ in dollars). Its opening eliminated the last traffic signal between Seattle and Portland. I-5 was routed around Bellingham on an easterly arc with several interchanges that were added after lobbying by downtown business groups who had originally favored a waterfront route. The first section, long and four lanes wide, opened to traffic on December 5, 1960, connecting with an existing expressway to Ferndale. The remainder of I-5 from Ferndale to the Peace Arch border crossing was upgraded in two stages, beginning with to Dakota Creek near Blaine that opened on October 29, 1963. The last section through Blaine was delayed by construction issues and opened on November 23, 1965, with a dedication ceremony at the Peace Arch. The British Columbian government had already completed upgrades to its section of
Highway 99 between Blaine and the Fraser River in 1962. The southernmost section of the Bellingham Freeway through the Chuckanut Mountains opened in three stages in 1966, completing the last four-lane section of the highway in the state. The section between north Seattle and Everett was opened on February 3, 1965. It was constructed over sections of the former Seattle–Everett Interurban Railway and cost $23 million (equivalent to $ in dollars). Several of the freeway's interchanges in southern Snohomish County were opened two months later. The freeway was initially six lanes wide but was expanded to eight lanes from Northgate to modern-day Shoreline in 1966 because of increased traffic congestion. The bypass of downtown Everett between 41st Street and the Snohomish River was completed on January 18, 1968; its opening eliminated fourteen traffic lights and included ramps to connect with the Hewitt Avenue Trestle. The final section of I-5 was opened on May 14, 1969, spanning between Everett and Marysville over the Snohomish River delta. It was originally scheduled to open several months earlier, but delayed steel work on the bridge over the Snohomish River caused scheduling issues. Several
right-in/right-out intersections and non-grade-separated sections remained on I-5 until the completion of widening and grade separation projects in the 1970s. The section between northern Kelso and Castle Rock was improved to Interstate standards and widened to six lanes in 1976, which was followed by an expansion through Kelso that opened in 1981. The Kelso expansion project included relocating the freeway away from a mudslide-prone hill, transferring maintenance of the old alignment to the city government. A similar six-lane expansion project in Marysville in the late 1960s was delayed after a dispute between the state government and
Tulalip Tribes over compensation for land that was later settled in 1970. A section further north of Marysville was expanded to six lanes in 1972, including a new bridge over the Stillaguamish River for northbound traffic and replacement of a railroad underpass with a pair of overpasses.
Seattle planning and construction in north Seattle, pictured in 1963 A municipal traffic plan from 1946 outlined designs for a north–south freeway through Seattle that was later refined into the early concepts for Interstate 5 in the 1950s. A design from 1954 proposed an eight-lane facility from Downtown Seattle to
Ravenna that would cost $194 million (equivalent to $ in dollars) to construct. Alternate plans would have placed the freeway further east on 12th Avenue in Capitol Hill or along
Empire Way, which would later be used for the proposed
R. H. Thomson Expressway. A larger, twelve-lane freeway through Downtown Seattle with a reversible express lane system was announced in April 1957 ahead of a series of
public hearings. The proposal received a mix of strong support and criticism from members of the public, while the city government endorsed the plan with a caveat that
right of way along the freeway be reserved for use by
rapid transit. The twelve-lane design, sans transit, was approved the following year by the Bureau of Public Roads, allowing for property acquisition to begin. A dedicated office was created to handle property acquisition, which would require 4,500
parcels of land, and 10 percent were condemned by the government. The first section of the freeway within Seattle to be built was the
Ship Canal Bridge, a double-decker bridge over the
Lake Washington Ship Canal between the
University District and
Eastlake, which began construction in August 1958. Construction of the freeway through Downtown Seattle was delayed after 100 citizens marched on June 1, 1961, in protest of the "trench" design and sought to add a lidded tunnel with a rooftop park. The proposed design change was deferred for later consideration, but delayed the start of construction south of Olive Way to the following year. Land acquisition for the downtown section of I-5 was completed in June 1962 after a series of condemnations were settled by the
King County Superior Court. Demolition of buildings along the block-wide right-of-way had already begun, including the
Kalmar Hotel (built in 1881), which pre-dated the
Great Seattle Fire, and the Seventh Avenue Fire Hall (built in 1890), the oldest public building in the city. The demolitions were opposed by local preservationists, among them architects
Victor Steinbrueck and
Paul Thiry, but proceeded as planned. Seattle's Chinatown was divided by the construction of I-5, which resulted in the formation of a special district to preserve the neighborhood's Asian American heritage. The Ship Canal Bridge and of freeway between Ravenna Boulevard and Roanoke Street were dedicated and opened to traffic on December 18, 1962. The bridge cost $14 million to construct (equivalent to $ in dollars) and was among the largest ever built in the Pacific Northwest. After the opening of the
Evergreen Point Floating Bridge on August 28, 1963, traffic from the bridge was permitted to use a section of I-5 between SR 520 and Mercer Street. Traffic from the North Seattle section, which had been extended north from Ravenna Boulevard to
Bothell Way (SR 522), was diverted until a through connection was opened on November 12. The section in the Ravenna neighborhood also included a 300-person
fallout shelter under the freeway at Weedin Place that was completed in 1963 and later used for records storage before its abandonment. Some sections of the extensive
retaining walls along I-5 were pre-assembled at a plant in
Woodinville and hoisted in place by a crane to reduce working hours in residential neighborhoods. and the
Seattle Convention Center The remaining downtown section and approaches from the suburbs remained scheduled to be completed by 1967, with the state legislature passing a provision in a spending bill to accelerate construction. The delayed timeline was blamed by the Department of Highways on several uncontrollable factors, among them landslides along Beacon Hill and Capitol Hill, unfavorable weather, a cement masons strike, and relocation of utilities. The section between Olive Way and Mercer Street opened to limited traffic on October 30, 1964, with two northbound lanes to bypass congestion at the Mercer Street interchange. Two additional downtown interchanges at University Street and Cherry Street opened on June 30, 1966. Access to the northbound lanes of I-5 was extended to South Dearborn Street in late September 1966, while opening of the southbound section was delayed because of issues with the Airport Way exit. The Connecticut Street interchange, intended to be part of I-90 and connected to the Alaskan Way Viaduct, was partially constructed as part of the downtown section of I-5 but was left unfinished until 1991. The remainder of the Seattle section, a stretch from Midway to Olive Way, was opened to traffic on January 31, 1967, by Governor
Dan Evans. The reversible express lane system was built along with the rest of I-5 through Seattle and opened in separate phases. The first section of reversible lanes opened on June 2, 1965, with 13 access ramps between Olive Way and Northgate Mall. The express lanes were managed using a series of ramp barriers that were remotely controlled and monitored by eleven
closed-circuit television cameras that were activated in September 1965. An additional ramp at the Mercer Street interchange opened in October 1966 after southbound traffic was diverted to a new set of ramps. The southernmost section of the express lanes, including ramps to Columbia and Cherry streets at 5th Avenue, opened on January 31, 1967.
Major projects and expansions , looking south The First Hill Improvement Club and architect Paul Thiry led a campaign in 1961 to reconnect areas of Seattle severed by the freeway with lids that would house parks,
parking garages, and other buildings through leased
air rights. The lid proposal was approved in October 1969 with funding split between the local government, state government, the
Forward Thrust bonds program, and a private developer. Landscape architects
Lawrence Halprin and
Angela Danadjieva were selected to design the park lid and adjoining parking garages, which would incorporate
Brutalist elements and a series of
waterfalls. The
Freeway Park opened on July 4, 1976, incorporating pedestrian and open spaces between Seneca and University streets that continued up the northwest slope of First Hill. The
Washington State Convention and Trade Center (now the Seattle Convention Center) was constructed north of Freeway Park over a section of I-5 and opened in 1988. Part of the convention center complex was designed by Danadjieva as a continuation of Freeway Park, while the main structure rested on a series of trusses over I-5. In 2019, the Seattle city government approved funding for a feasibility study for an expanded downtown lid after lobbying from a
grassroots campaign. The
I-5 Colonnade, a
mountain bike park, opened in 2007 under an elevated section of the freeway between Eastlake and Capitol Hill. WSDOT began installing
ramp meters in 1981 to address worsening onramp congestion on I-5 from Seattle to Mountlake Terrace. The first set of 16 ramp meters were activated on September 30, 1981, with a computer system controlling entry at 5–15 second increments; some ramps also had un-metered bypass lanes for transit and three-person
carpools. The state's first set of
HOV lanes opened in August 1983 for use by buses and carpools from Northgate to Mountlake Terrace. By the late 1980s, the of HOV lanes had reduced average travel times on I-5 by four minutes despite an 86 percent increase in traffic volumes. The HOV lanes were extended north to Lynnwood in 1996 and southern Everett by the end of the decade, while the carpool minimum was lowered to two people per vehicle. In the 1970s, the state government began planning extensive rebuilding of the oldest sections of I-5 to meet newer Interstate standards and eliminate design issues. The , four-lane section through Tumwater, Olympia, and Lacey was rebuilt in the 1980s at a cost of $164 million (equivalent to $ in dollars). The freeway project was completed in late 1991 with an expansion to six lanes, six rebuilt interchanges, a new bridge for Capitol Way, and improved landscaping. The existing Pacific Avenue interchange near the Tacoma Dome was expanded in the 1980s to accommodate
I-705, a new spur freeway traveling north to downtown Tacoma. The rebuilding of the Vancouver section was completed in August 1983 at a cost of $40 million (equivalent to $ in dollars). It included widening the freeway to six lanes, new interchanges with SR 14 and SR 500, relocation of railroad tracks, and the replacement of several overpasses. An additional expansion project on I-5 through Vancouver and Hazel Dell was completed in 2001, replacing the original overpasses and adding a southbound HOV lane. The HOV lane was later removed in 2005 after drivers complained about increased travel times for single-occupant vehicles. A second widening project, completed in 2006, added two lanes on a from Hazel Dell to the I-205 interchange in Salmon Creek, where a new ramp to Northeast 139th Street was later opened in 2014. , featuring HOV lanes and sound walls In April 2003, the state legislature passed the
Nickel Funding Package, which enacted a five-cent gas tax increase to fund $4.2 billion in transportation projects (equivalent to $ in dollars) that were rejected in an earlier public
referendum. The program funded several projects to widen and modernize sections of I-5, including new interchanges in Clark County and the extension of HOV lanes in Everett and from Tukwila to Tacoma. Several direct access ramps for the HOV lanes were constructed in the 2000s using funds from
Sound Transit to serve bus facilities in Lynnwood and Federal Way. The Everett expansion project cost $263 million to construct and consisted of HOV lanes from the Everett Mall to the Snohomish River, realigned ramps, a new single-point urban interchange at 41st Street, and a reconstructed Broadway interchange with HOV ramps and a flyover ramp. Construction began in September 2005 under a
design–build contract, the third in WSDOT's history, and was completed in June 2008 as part of an accelerated timeline to prepare for the
2010 Winter Olympics hosted by Vancouver, British Columbia. The southern end of the HOV lanes on I-5 in King County was extended to SR 516 in 1995 and Federal Way in 2007 using Nickel Package funding. Construction of an HOV lane system through Tacoma, which would also include a new interchange with SR 16 and the Nalley Valley Viaduct, began in 2001 with the replacement of the South 38th Street overpass to accommodate a wider freeway. The Tacoma/Pierce County HOV program launched with partial funding for the $1.6 billion
megaproject that was later filled with an
earmark in the state legislature's 2005 transportation funding package. Construction on the HOV lanes began in 2009 with an extension through Fife to Port of Tacoma Road and
seismic retrofitting of bridges that was completed two years later. The reconstructed SR 16 opened in two phases, with the new westbound viaduct carrying all between its opening in June 2011 and the completion of the eastbound viaduct in August 2014. A set of ramps connecting the HOV lanes of I-5 and SR 16 on the Nalley Valley Viaduct opened in November 2019. WSDOT broke ground on the longest section of the Tacoma HOV program, spanning from SR 16 to Port of Tacoma Road, in July 2014. The reconstructed section was completed in November 2018 with a new set of collector–distributor lanes, a carriageway for the northbound lanes of I-5 through the I-705 interchange, the replacement of two overpasses, and extended
retaining walls for excavated areas. WSDOT began the final phase of the project, replacement of the Puyallup River crossing with wider bridges on a straighter alignment, in February 2015. The northbound bridge was completed in October 2017 and all traffic was shifted to it beginning in June 2019. The southbound bridge was opened to traffic in April 2022 and the HOV lanes were fully opened from Fife to SR 16 in late August. The 2003 and 2005 gas tax programs also funded improvements to I-5 in areas outside of the central Puget Sound region, including $322 million for lane expansions on a corridor in Lewis and Thurston counties. The existing four-lane section from US 12 in Grand Mound to SR 121 in Maytown gained a third lane in each direction that opened in November 2010 at a cost of $61.5 million. The following year, the six-lane section was extended south by to Blakeslee Junction near Centralia. Widening of the section through Centralia to six lanes was completed in 2016 and also included the addition of collector–distributor lanes, three reconstructed interchanges, and flood control measures. A section of the freeway from Chehalis to Grand Mound had closed for four days during
December 2007 floods that covered the roadway in of water from the Chehalis River. WSDOT was also allocated funding from the 2003 and 2005 packages to repair bridges on I-5 and add
cable barriers to sections of I-5 in Lewis, Skagit, Snohomish, and Whatcom counties. A section through Marysville was later upgraded to a concrete barrier in 2010 after several fatal crossover collisions despite a reduction in the speed limit to . Other parts of the packages funded seismic retrofitting for bridges and overpasses, and the implementation of
smart highway technology in 2010 that included
variable speed limit signs in the Seattle area. In May 2023, a third northbound lane from Seneca Street to Olive Way and ramp meters for the collector–distributor lanes and the Cherry Street onramp were added to I-5 to improve weaving.
Incidents and closures over southbound I-5 in
DuPont On May 23, 2013, the northernmost span of the
Skagit River bridge between Mount Vernon and Burlington
collapsed after a
semi-trailer truck struck an overhead beam. The collapse caused two vehicles to fall into the river, where all three people were later rescued with minor injuries. The incident triggered a
state of emergency and discussions about the state of national infrastructure. A temporary span was assembled using prefabricated steel sections and opened to limited traffic on June 19, 2013. A permanent replacement for the span was built west of the bridge and slid into place before opening to traffic on September 15, 2013. A section of I-5 was closed for several hours on December 18, 2017, after an Amtrak
Cascades passenger train
derailed onto the southbound lanes near DuPont. The train had been on the inaugural trip on the new
Point Defiance Bypass route, constructed along the freeway between
Nisqually and
Tacoma Dome Station, which was subsequently closed. The derailment, which killed three passengers and injured more than 70 others, was caused by high speeds on a curved section of track approaching the I-5 overpass. The Seattle section of I-5 has been the site of several large protests and demonstrations since its construction. A demonstration against the
U.S. invasion of Cambodia at the University of Washington on May 5, 1970, held in response to the
Kent State shootings, culminated in 5,000 protesters marching onto the Ship Canal Bridge en route to Downtown Seattle. An attempted protest on the freeway the following day was stopped by local police and state troopers armed with
tear gas and clubs. The city government sanctioned a march in the express lanes on May 8 that was attended by 15,000 people as other protests continued for several days. The
1999 WTO Conference protests included minor disruptions to I-5 traffic while police blocked access from ramps in Downtown Seattle. Several
Black Lives Matter protests in 2014, 2016, and 2020 resulted in long nighttime shutdowns of the freeway in Seattle and Olympia. The 2020
George Floyd protests included over a month of nightly protests on I-5 with a non-intervention policy implemented by the Washington State Patrol and precautionary closures. The non-intervention policy was suspended after a July 4 incident in which a driver evaded the blockades and struck two protesters on I-5, killing one.
Future projects and proposals , a pair of movable bridges that carry I-5 over the
Columbia River, are planned to be replaced in the 2020s Within the Puget Sound region, preservation and maintenance of I-5 is expected to cost $2.5 billion between 2020 and 2040, and substantial rebuilding of the freeway will be required. WSDOT began extensive repaving of the highway in the Seattle area in the 2010s, alongside repairs to
expansion joints and other deteriorating structures during weekend closures. Pavement replacement and expansion joint repairs on the section between Yesler Way and North 117th Street in Seattle is expected to begin in 2023 and take four years to complete. Portions of the freeway's
right-of-way will be used for extensions of Sound Transit's
Link light rail system, which is planned to extend north to Lynnwood and south to Federal Way by 2025. As part of the reconstruction of
SR 520, a new HOV ramp from the I-5 reversible lanes to SR 520 is planned to be opened in early 2024, alongside a fifth reversible lane for HOVs that extends south to Mercer Street. The 2015 Connecting Washington transportation funding package included allocations for several major projects on I-5, among them an expansion in the Joint Base Lewis–McChord area and several new and reconstructed interchanges in Lacey and Marysville. Widening of an section through the military base and neighboring DuPont to eight lanes began in October 2018 and is planned to be completed in 2025; the project also includes reconstruction of several interchanges and accommodations for the adjacent Point Defiance Bypass railroad corridor. The
SR 510 interchange in Lacey was reconstructed into the state's first
diverging diamond interchange, which opened in 2020. The northbound HOV lane is planned to be extended from Everett to Marysville by late 2024 as part of a $123 million retrofit project that began construction in 2022. It will also include an expansion of the SR 529 interchange in southern Marysville into a full interchange to provide a bypass for a congested railroad crossing on SR 528. A new interchange at 156th Street in northern Marysville is planned to open in the late 2020s. The Puget Sound Gateway Program, scheduled to be completed in 2028 will include the construction of two interchanges on I-5, at the Port of Tacoma to serve a realigned SR 167 and near SeaTac for an extension of
SR 509. The Vancouver section of I-5 was planned to be rebuilt as part of the
Columbia River Crossing program, which would have replaced the six-lane
Interstate Bridge with a wider bridge at a cost of approximately $3.4 billion. The northern approach to the bridge would have included a collector–distributor system with a maximum width of 16 lanes. The program was cancelled in 2013 after $175 million had been spent planning because of opposition within the Washington state legislature, but the bridge proposal has been revived several times since. A new panel of legislators from both states was convened in 2018 to study the bridge project, with funding to continue planning work in time for federal deadlines on loan repayment. Oregon and Washington plan to submit an environmental review in 2023 and begin construction in 2025 if funding is found for the project. The bridge replacement is expected to cost up to $2.45 billion, while the entire program—including reconstruction of several interchanges and transit improvements—is estimated to cost $5.5 billion to $7.5 billion. ==Exit list==