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Interstate 5 (I-5) is an
Interstate Highway The Dwight D. Eisenhower National System of Interstate and Defense Highways, commonly known as the Interstate Highway System, is a network of controlled-access highways that forms part of the National Highway System in the United States. T ...
on the
West Coast of the United States The West Coast of the United States, also known as the Pacific Coast, Pacific states, and the western seaboard, is the coastline along which the Western United States meets the North Pacific Ocean. The term typically refers to the contiguous U.S ...
that serves as the region's primary north–south route. It spans across the state of
Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...
, from the
Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...
state border at
Vancouver Vancouver ( ) is a major city in western Canada, located in the Lower Mainland region of British Columbia. As the most populous city in the province, the 2021 Canadian census recorded 662,248 people in the city, up from 631,486 in 2016. ...
, through the
Puget Sound region The Puget Sound region is a coastal area of the Pacific Northwest in the U.S. state of Washington, including Puget Sound, the Puget Sound lowlands, and the surrounding region roughly west of the Cascade Range and east of the Olympic Mountains. ...
, to the
Canadian border Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of ...
at Blaine. Within the
Seattle metropolitan area The Seattle metropolitan area is an urban conglomeration in the U.S. state of Washington that comprises Seattle, its surrounding satellites and suburbs. It contains the three most populous counties in the state—King, Snohomish, and Pierce ...
, the freeway connects the cities of Tacoma,
Seattle Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest region o ...
, and Everett. I-5 is the only interstate to traverse the whole state from north to south and is Washington's busiest highway, with an average of 274,000 vehicles traveling on it through
Downtown Seattle Downtown is the central business district of Seattle, Washington. It is fairly compact compared with other city centers on the U.S. West Coast due to its geographical situation, being hemmed in on the north and east by hills, on the west by ...
on a typical day. The segment in Downtown Seattle is also among the widest freeways in the United States, at 13 lanes, and includes a set of express lanes that reverse direction depending on time of the day. Most of the freeway is four lanes in rural areas and six to eight lanes in suburban areas, utilizing a set of
high-occupancy vehicle lane A high-occupancy vehicle lane (also known as an HOV lane, carpool lane, diamond lane, 2+ lane, and transit lane or T2 or T3 lanes) is a restricted traffic lane reserved for the exclusive use of vehicles with a driver and one or more passengers, i ...
s in the latter. I-5 also has three related auxiliary Interstates in the state,
I-205 Interstate 205 may refer to either of two unconnected Interstate Highways in the United States, both of which are related to Interstate 5 * Interstate 205 (California), a connector in the San Francisco Bay Area * Interstate 205 (Oregon–Washin ...
, I-405, and I-705, as well as several designated
business routes A business route (or business loop, business spur, or city route) in the United States is a short special route connected to a ''parent'' numbered highway at its beginning, then routed through the central business district of a nearby city ...
and state routes. The freeway follows several historic railroads and wagon trails developed during American settlement of
western Washington Western Washington is a region of the United States defined as the area of Washington state west of the Cascade Mountains. This region is home to the state's largest city, Seattle, the state capital, Olympia, and most of the state's residents. T ...
in the mid-to-late 19th century. The
state legislature A state legislature is a legislative branch or body of a political subdivision in a federal system. Two federations literally use the term "state legislature": * The legislative branches of each of the fifty state governments of the United Sta ...
incorporated local roads into the Pacific Highway in 1913, connecting the state's southern and northern borders between Vancouver and Blaine. The Pacific Highway was built and paved over the next decade, and became the northernmost segment of the national U.S. Route 99 (US 99) in 1926. The federal government endorsed the creation of a national expressway system in the 1940s, including several bypasses on US 99 that were built by the state in the early 1950s. The state's planned toll superhighway in the Seattle area was shelved in favor of a federally-funded freeway under the new Interstate Highway System, under which I-5 was created in 1957. Construction of I-5 was completed in 1969, and several segments of the highway have been widened or improved in the decades since.


Route description

Interstate 5 is the only Interstate to traverse Washington from north to south, serving as the primary highway for the
western Western may refer to: Places *Western, Nebraska, a village in the US *Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a locality in Australia *Western world, countries that id ...
portion of the state. It is listed as part of the National Highway System and the state's Highways of Statewide Significance program, recognizing its connection to major communities. I-5 has three
auxiliary Interstate Highways Auxiliary may refer to: * A backup site or system In language * Auxiliary language (disambiguation) * Auxiliary verb In military and law enforcement * Auxiliary police * Auxiliaries, civilians or quasi-military personnel who provide support of ...
within Washington:
I-205 Interstate 205 may refer to either of two unconnected Interstate Highways in the United States, both of which are related to Interstate 5 * Interstate 205 (California), a connector in the San Francisco Bay Area * Interstate 205 (Oregon–Washin ...
, an easterly bypass of
Portland, Oregon Portland (, ) is a port city in the Pacific Northwest and the largest city in the U.S. state of Oregon. Situated at the confluence of the Willamette and Columbia rivers, Portland is the county seat of Multnomah County, the most populous ...
, and
Vancouver Vancouver ( ) is a major city in western Canada, located in the Lower Mainland region of British Columbia. As the most populous city in the province, the 2021 Canadian census recorded 662,248 people in the city, up from 631,486 in 2016. ...
; I-405, bypassing
Seattle Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest region o ...
via the Eastside; and I-705, a short spur into Tacoma., wit
inset maps
It was designated as the
Purple Heart The Purple Heart (PH) is a United States military decoration awarded in the name of the President to those wounded or killed while serving, on or after 5 April 1917, with the U.S. military. With its forerunner, the Badge of Military Merit, ...
Trail in 2013 by the Washington State Transportation Commission to honor wounded military veterans. The freeway runs through the most densely populated region of Washington state, with 4.6 million people living in the nine counties on the corridor, approximately 70 percent of the state's population. Several of the largest cities along the I-5 corridor are also connected by the parallel ''Cascades'', a regional train service between
Eugene, Oregon Eugene ( ) is a city in the U.S. state of Oregon. It is located at the southern end of the Willamette Valley, near the confluence of the McKenzie and Willamette rivers, about east of the Oregon Coast. As of the 2020 United States Census, ...
, and
Vancouver Vancouver ( ) is a major city in western Canada, located in the Lower Mainland region of British Columbia. As the most populous city in the province, the 2021 Canadian census recorded 662,248 people in the city, up from 631,486 in 2016. ...
, British Columbia, operated by
Amtrak The National Railroad Passenger Corporation, doing business as Amtrak () , is the national passenger railroad company of the United States. It operates inter-city rail service in 46 of the 48 contiguous U.S. States and nine cities in Canada. ...
and funded by the state governments of Oregon and Washington. I-5 is maintained by the
Washington State Department of Transportation The Washington State Department of Transportation (WSDOT or WashDOT, both ) is a governmental agency that constructs, maintains, and regulates the use of transportation infrastructure in the U.S. state of Washington. Established in 1905, it is ...
(WSDOT), who conduct an annual survey of traffic volume that is expressed in terms of
average annual daily traffic Annual average daily traffic, abbreviated AADT, is a measure used primarily in transportation planning, transportation engineering and retail location selection. Traditionally, it is the total volume of vehicle traffic of a highway or road for a ...
(AADT), a measure of traffic volume for any average day of the year. The stretch of I-5 through
Downtown Seattle Downtown is the central business district of Seattle, Washington. It is fairly compact compared with other city centers on the U.S. West Coast due to its geographical situation, being hemmed in on the north and east by hills, on the west by ...
is the busiest highway in Washington state, with a daily average of over 274,000 vehicles in the mainline and express lanes. The least-traveled segment of I-5 is located at SR 548 in Blaine, with a daily average of 6,600 vehicles. I-5 through the
Seattle metropolitan area The Seattle metropolitan area is an urban conglomeration in the U.S. state of Washington that comprises Seattle, its surrounding satellites and suburbs. It contains the three most populous counties in the state—King, Snohomish, and Pierce ...
is among the worst congested highways in the United States, with 78 percent of peak direction miles classified as "routinely congested" for seven to eight hours a day and an average annual delay of 55 hours for Seattle– Everett commutes. The freeway has a maximum
speed limit Speed limits on road traffic, as used in most countries, set the legal maximum speed at which vehicles may travel on a given stretch of road. Speed limits are generally indicated on a traffic sign reflecting the maximum permitted speed - expre ...
of in rural areas and in urban and suburban areas, which includes a section between
Tumwater Tumwater is a town in Thurston County, Washington, United States. The population was 25,350 at the 2020 census. It is situated near where the Deschutes River enters Budd Inlet, the southernmost point of Puget Sound; it also borders the state ...
and Marysville.


Southwestern Washington

I-5 enters Washington on the
Interstate Bridge The Interstate Bridge (also Columbia River Interstate Bridge, I-5 Bridge, Portland-Vancouver Interstate Bridge, Vancouver-Portland Bridge) is a pair of nearly identical steel vertical-lift, Parker through-truss bridges that carry Interstate 5 ...
, a pair of
vertical-lift bridge A vertical-lift bridge or just lift bridge is a type of movable bridge in which a span rises vertically while remaining parallel with the deck. The vertical lift offers several benefits over other movable bridges such as the bascule and sw ...
s that span the
Columbia River The Columbia River ( Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia ...
between Portland, Oregon, and Vancouver, Washington. The bridge is the only point on I-5 where vehicles have to stop for cross traffic, due to the lifts. On the north bank of the river, the freeway passes under a railroad viaduct carrying Amtrak's ''
Empire Builder The ''Empire Builder'' is an Amtrak long-distance passenger train that operates daily between Chicago and either Seattle or Portland via two sections west of Spokane. Introduced in 1929, it was the flagship passenger train of the Great Northe ...
'' and intersects SR 14. The interchange with SR 14, located west of
Pearson Field Pearson Field also once known as Pearson Airpark, is a city-owned municipal airport located one mile (2 km) southeast of the central business district of Vancouver, a city in Clark County, Washington, United States. Pearson Field is t ...
and the
Fort Vancouver National Historic Site Fort Vancouver National Historic Site is a United States National Historic Site located in the states of Washington and Oregon. The National Historic Site consists of two units, one located on the site of Fort Vancouver in modern-day Vancouve ...
, also includes ramps serving downtown Vancouver. I-5 continues north through suburban Vancouver and into Hazel Dell, passing the
Clark College Clark College is a public community college in Vancouver, Washington. With 11,500 students, Clark College is the largest institution of higher education in southwest Washington. Founded in 1933 as a private two-year junior college, Clark Colleg ...
campus and intersecting SR 501 at Fourth Plain Boulevard and SR 500 at Burnt Bridge Creek. I-5 intersects
I-205 Interstate 205 may refer to either of two unconnected Interstate Highways in the United States, both of which are related to Interstate 5 * Interstate 205 (California), a connector in the San Francisco Bay Area * Interstate 205 (Oregon–Washin ...
, the eastern freeway bypass of the
Portland metropolitan area The Portland metropolitan area is a metro area in the U.S. states of Oregon and Washington centered on the principal city of Portland, Oregon. The U.S. Office of Management and Budget (OMB) identifies it as the Portland–Vancouver–Hillsboro, ...
, in Salmon Creek near the Vancouver campus of
Washington State University Washington State University (Washington State, WSU, or informally Wazzu) is a public land-grant research university with its flagship, and oldest, campus in Pullman, Washington. Founded in 1890, WSU is also one of the oldest land-grant uni ...
. From Salmon Creek, I-5 continues northwesterly and intersects SR 502 at the Gee Creek
rest area A rest area is a public facility located next to a large thoroughfare such as a motorway, expressway, or highway, at which drivers and passengers can rest, eat, or refuel without exiting onto secondary roads. Other names include motorway serv ...
west of Battle Ground. Its next interchange, in eastern Ridgefield, forms the eastern terminus of SR 501. The freeway passes the
Ilani Casino Resort The ilani Casino Resort ( ) is a casino operated by the Cowlitz Indian Tribe and located near La Center, Washington. The casino opened on April 24, 2017, after a lengthy legal battle over the tribe's right to establish a reservation on which to ...
on the Cowlitz reservation and crosses the Lewis River into
Woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the '' plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...
, where it intersects SR 503. Northwest of Woodland, the
median In statistics and probability theory, the median is the value separating the higher half from the lower half of a data sample, a population, or a probability distribution. For a data set, it may be thought of as "the middle" value. The basic f ...
of I-5 is used by freight trains and Amtrak's ''Cascades'' and ''
Coast Starlight The ''Coast Starlight'' is a passenger train operated by Amtrak on the West Coast of the United States between Seattle and Los Angeles via Portland and the San Francisco Bay Area. The train, which has operated continuously since Amtrak's format ...
'' passenger trains, which follow the freeway for its entire length. I-5 continues along the east bank of the Columbia River, passing through Kalama on the way towards Longview and Kelso. At the south end of Kelso, near the confluence of the Columbia and
Cowlitz Cowlitz may refer to: People * Cowlitz people, an indigenous people of the Pacific Northwest ** Cowlitz language, member of the Tsamosan branch of the Coast Salish family of Salishan languages * Cowlitz Indian Tribe, a federally recognized tribe o ...
rivers, the freeway intersects SR 432, which connects to Longview and the Lewis and Clark Bridge via SR 433. I-5 continues north along the
Coweeman River The Coweeman River is a tributary of the Cowlitz River, in the South West corner of the U.S. state of Washington. Its name comes from the Cowlitz word ko-wee-na, meaning "short one", referring to a short Indian who once lived along the river. Co ...
to the
Three Rivers Mall Three Rivers Mall is an enclosed shopping mall located in Kelso, Washington that opened in 1987, on the site of a former golf course adjacent to Interstate 5. Previously owned by General Growth Properties, the mall was one of 30 malls that was sp ...
, located east of downtown Kelso, where SR 4 terminates. Between Vancouver and Kelso, the highway is part of the
Lewis and Clark Trail The Lewis and Clark National Historic Trail is a route across the United States commemorating the Lewis and Clark Expedition of 1804 to 1806. It is part of the National Trails System of the United States. It extends for some from Pittsburgh, ...
, a state scenic highway that continues west along SR 4 towards the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...
. The freeway continues north, following the Cowlitz River to Castle Rock, where it meets SR 411 and a short
business route A business route (or business loop, business spur, or city route) in the United States is a short special route connected to a ''parent'' numbered highway at its beginning, then routed through the central business district of a nearby city ...
that loops back to an interchange with SR 504, the main highway to Mount St. Helens. North of Castle Rock, the Cowlitz River turns away from I-5 as the latter enters Lewis County, intersecting SR 506 west of Toledo and SR 505 east of Winlock. Between the two interchanges is the
Gospodor Monument Park Gospodor Monument Park is a roadside attraction along Interstate 5 in Washington, Interstate 5 near Toledo, Washington, in the United States. It features four sculptures, collectively known as the Gospodor monuments, created in 2002. The tallest s ...
, a
roadside attraction A roadside attraction is a feature along the side of a road meant to attract tourists. In general, these are places one might stop on the way to somewhere, rather than actually being a destination. They are frequently advertised with billboards. ...
with four sculptures of up to in height commemorating religious and indigenous figures. After their installation in 2002, the sculptures caused backups on the freeway due to
rubbernecking Rubbernecking is a derogatory term primarily used to refer to bystanders staring at accidents. More generally, it can refer to anyone staring at something of everyday interest compulsively (especially tourists). The term ''rubbernecking'' derive ...
by passing drivers who slowed down near them. Near Napavine, I-5 becomes concurrent with US 12, which continues east across White Pass to Yakima. The two highways intersect SR 508 and cross over the Newaukum River near the
Uncle Sam billboard The Uncle Sam billboard is a large, privately owned billboard in Washington State which displays messages of political commentary. The billboard is located directly adjacent to the northbound lanes of Interstate 5 in Napavine, Washington, arou ...
, a politically conservative message board and roadside attraction. I-5 and US 12 turn northwest to follow the river and pass along the western edge of Chehalis, where they intersect SR 6. After passing the Chehalis-Centralia Airport, the freeway follows the Chehalis River to the western side of
Centralia Centralia may refer to: Places Australia *Central Australia, sometimes called "Centralia" Canada * Centralia, Ontario ** RCAF Station Centralia, a former Royal Canadian Air Force training base ** Centralia (Essery Field) Aerodrome United State ...
. I-5 and US 12 then intersect SR 507 and gain a set of collector–distributor lanes as the freeway crosses the
Skookumchuck River The Skookumchuck River is a long river located in southwest Washington, United States. It is a tributary of the Chehalis River and thence to the Pacific Ocean. The Skookumchuck Dam was built in 1970, creating the Skookumchuck Reservoir. The d ...
and a set of railroad tracks on the northwest side of the city. US 12 leaves the concurrency at Grand Mound, heading west towards
Aberdeen Aberdeen (; sco, Aiberdeen ; gd, Obar Dheathain ; la, Aberdonia) is a city in North East Scotland, and is the third most populous city in the country. Aberdeen is one of Scotland's 32 local government council areas (as Aberdeen City), a ...
while I-5 continues north into Thurston County.


South Sound region

North of Grand Mound, I-5 passes two interchanges with SR 121, which forms a loop between two of the exits to serve
Millersylvania State Park Millersylvania State Park is a public recreation area located on Deep Lake south of Olympia, Washington. The state park's include old-growth cedar and fir trees as well as of freshwater shoreline. In 2009, the park was listed on the National ...
. The freeway travels through the suburb of Tumwater, passing the
Olympia Regional Airport Olympia Regional Airport is a public use airport located four nautical miles (7 km) south of the central business district of Olympia, a city in Thurston County and the capital of the U.S. state of Washington. It is owned by the Port of O ...
and several state
office park A business park or office park is a designated area of land in which many office buildings are grouped together. These types of developments are often located in suburban areas where land and building costs are more affordable, and are typically ...
s before reaching the terminus of US 101, a major highway that encircles the
Olympic Peninsula The Olympic Peninsula is a large arm of land in western Washington that lies across Puget Sound from Seattle, and contains Olympic National Park. It is bounded on the west by the Pacific Ocean, the north by the Strait of Juan de Fuca, a ...
, on the south side of
Capitol Lake Capitol Lake is a 3 kilometer (1.9 mile) long, artificial lake at the mouth of Deschutes River in Tumwater/Olympia, Washington. The Olympia Brewery sits on Capitol Lake in Tumwater, just downstream from where the Tumwater Falls meet the art ...
. After the interchange, I-5 enters Olympia and turns eastward after passing the
Washington State Capitol The Washington State Capitol or ''Legislative Building'' in Olympia is the home of the government of the state of Washington. It contains chambers for the Washington State Legislature and offices for the governor, lieutenant governor, secretary ...
campus and downtown Olympia. The freeway passes through
Lacey Lacey may refer to: People Surname A–L * Andrew Lacey (1887–1946), Australian politician * Bill Lacey (American football) (born 1971), American football player and coach * Bill Lacey (footballer) (1889–1969), Irish footballer * Bob Lacey ( ...
and the Hawks Prairie industrial area, where it intersects SR 510, a highway serving the Nisqually Indian Community and Yelm. I-5 continues northeast through the Billy Frank Jr. Nisqually National Wildlife Refuge towards
DuPont DuPont de Nemours, Inc., commonly shortened to DuPont, is an American multinational chemical company first formed in 1802 by French-American chemist and industrialist Éleuthère Irénée du Pont de Nemours. The company played a major role in ...
on the east side of the
Nisqually River The Nisqually River is a river in west central Washington in the United States, approximately long. It drains part of the Cascade Range southeast of Tacoma, including the southern slope of Mount Rainier, and empties into the southern end of Pu ...
in Pierce County. Immediately east of DuPont, I-5 travels through
Joint Base Lewis–McChord Joint Base Lewis–McChord (JBLM) is a U.S. military installation home to I Corps and 62nd Airlift Wing located south-southwest of Tacoma, Washington under the jurisdiction of the United States Army Joint Base Headquarters, Joint Base Lewis–Mc ...
, a major military installation that encompasses land on both sides of the freeway and its parallel railroad. Near
American Lake American Lake is a lake located in Lakewood, Washington at Joint Base Lewis-McChord. It is the largest natural lake in Pierce County. There are two public parks on the large lake: American Lake North Park & Marina, and Harry Todd Park. Both have l ...
, an interchange with Thorne Lane marks the proposed western terminus of SR 704, a new highway that would travel between the boundaries of Fort Lewis and
McChord Air Force Base McChord Field is a United States Air Force base in the northwest United States, in Pierce County, Washington. South of Tacoma, McChord Field is the home of the 62d Airlift Wing, Air Mobility Command, the field's primary mission being worldw ...
(the two components of Joint Base Lewis–McChord) to Spanaway. Continuing past the bases, I-5 passes through Lakewood and intersects SR 512, an freeway connecting east to
Puyallup Puyallup may refer to: * Puyallup (tribe), a Native American tribe * Puyallup, Washington, a city ** Puyallup High School ** Puyallup School District ** Puyallup station, a Sounder commuter rail station ** Washington State Fair, formerly the ...
, before it reaches Tacoma. In Tacoma, the freeway passes the
Tacoma Mall The Tacoma Mall is the largest shopping center in Tacoma, Washington, and is owned and operated by the Simon Property Group. Anchor tenants include Dick's Sporting Goods, JCPenney (originally two levels, but added a third level in 1986), Macy's ( ...
, turns east, and splits into collector–distributor lanes that run through central Tacoma and serve two interchanges: the terminus of SR 16, which continues northwest over the Tacoma Narrows Bridge to the
Kitsap Peninsula The Kitsap Peninsula () lies west of Seattle across Puget Sound, in Washington state in the Pacific Northwest. Hood Canal separates the peninsula from the Olympic Peninsula on its west side. The peninsula, a.k.a. "Kitsap", encompasses all of Kit ...
; and I-705 and SR 7, which serve downtown Tacoma, the Tacoma Dome, Tacoma Dome Station, and the Pacific Avenue corridor. East of the Tacoma Dome area, I-5 intersects SR 167 and crosses over the
Puyallup River The Puyallup River ( ) is a river in the U.S. state of Washington. About long, it is formed by glaciers on the west side of Mount Rainier. It flows generally northwest, emptying into Commencement Bay, part of Puget Sound. The river and its tribu ...
and a railroad carrying Sounder commuter trains. The freeway reaches
Fife Fife (, ; gd, Fìobha, ; sco, Fife) is a council area, historic county, registration county and lieutenancy area of Scotland. It is situated between the Firth of Tay and the Firth of Forth, with inland boundaries with Perth and Kinross ...
on the
Puyallup Indian Reservation The Puyallup, Spuyalpabš or S’Puyalupubsh (pronounced: Spoy-all-up-obsh) ('generous and welcoming behavior to all people, who enter our lands') are a federally recognized Coast Salish Native American tribe from western Washington state, Un ...
and intersects SR 99, a section of former US 99, at 54th Avenue East near the
Emerald Queen Casino The Puyallup, Spuyalpabš or S’Puyalupubsh (pronounced: Spoy-all-up-obsh) ('generous and welcoming behavior to all people, who enter our lands') are a federally recognized Coast Salish Native American tribe from western Washington state, Un ...
. After crossing Hylebos Creek, I-5 turns north and ascends from the Puyallup River Valley, entering
King County King County is located in the U.S. state of Washington. The population was 2,269,675 in the 2020 census, making it the most populous county in Washington, and the 13th-most populous in the United States. The county seat is Seattle, also the st ...
and the city of
Federal Way Federal Way is a city in King County, Washington, United States. One of the most recently incorporated cities in the county, its population was 101,030 at the 2020 census. Federal Way is the tenth-largest city in Washington and the fifth-larg ...
while parallel to SR 99. After passing under SR 161 at Kitts Corner near the
Wild Waves Theme Park Wild Waves Theme & Water Park is an amusement park and water park in Federal Way, Washington. Opened in 1977 as The Enchanted Village (with its accompanying water park, Wild Waves, opening in 1984),''Washington State's Enchanted Parks Announces ...
, I-5 intersects SR 18, a freeway that connects to Auburn and Maple Valley. I-5 continues north past the former
Weyerhauser Weyerhaeuser () is an American timberland company which owns nearly of timberlands in the U.S., and manages an additional of timberlands under long-term licenses in Canada. The company also manufactures wood products. It operates as a real ...
headquarters campus to central Federal Way, where the freeway's
high-occupancy vehicle lane A high-occupancy vehicle lane (also known as an HOV lane, carpool lane, diamond lane, 2+ lane, and transit lane or T2 or T3 lanes) is a restricted traffic lane reserved for the exclusive use of vehicles with a driver and one or more passengers, i ...
s (HOV lanes) have a direct off-ramp to the
Federal Way Transit Center Federal Way Downtown is a future light rail station at the site of the Federal Way Transit Center, a bus station in Federal Way, Washington. The bus station opened in 2006 and has 1,190 parking spaces available in its parking garage and surface ...
and The Commons at Federal Way shopping mall. The freeway travels north into western
Kent Kent is a county in South East England and one of the home counties. It borders Greater London to the north-west, Surrey to the west and East Sussex to the south-west, and Essex to the north across the estuary of the River Thames; it faces ...
, intersecting SR 516 near Highline College. North of Angle Lake, I-5 tracks eastward between the cities of SeaTac and Tukwila, passing east of
Seattle–Tacoma International Airport Seattle–Tacoma International Airport , branded as SEA Airport and also referred to as Sea–Tac (), is the primary commercial airport serving the Seattle metropolitan area in the U.S. state of Washington. It is in the city of SeaTac, which ...
. At the Westfield Southcenter shopping mall in Tukwila, I-5 intersects SR 518, the primary means of access to the airport and
Burien Burien ( ) is a suburban city in King County, Washington, United States, located south of Seattle on Puget Sound. As of the 2020 census, Burien's population was 52,066, which is a 56.3% increase since incorporation in 1993. An annexation in 201 ...
, and I-405, the eastern freeway bypass of Seattle that travels through Renton and the Eastside. The interchange includes several left-hand ramps, necessitating the separation of the thru HOV lanes from the mainline. For a short distance, the light rail tracks of the Link 1 Line, which followed SR 518 from Tukwila International Boulevard station, join I-5 and run on its west side until the next interchange at SR 599, a short freeway that connects to SR 99. From the SR 599 interchange, I-5 makes a gradual turn to the northwest while crossing over the