State Route 509 (SR 509) is a

state highway A state highway, state road, or state route (and the equivalent provincial highway, provincial road, or provincial route) is usually a road that is either ''numbered'' or ''maintained'' by a sub-national state or province. A road numbered by a ...

in the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sover ...

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 on ...

, connecting Tacoma in Pierce County to

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 regio ...

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 ...

. The highway travels north from Interstate 705 (I-705) in Tacoma to SR 99 south of downtown Seattle. It serves cities along the

Puget Sound Puget Sound ( ) is a sound of the Pacific Northwest, an inlet of the Pacific Ocean, and part of the Salish Sea. It is located along the northwestern coast of the U.S. state of Washington. It is a complex estuarine system of interconnected ma ...

and west 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 ...

in south King County, including

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-larges ...

Des Moines Des Moines () is the capital and the most populous city in the U.S. state of Iowa. It is also the county seat of Polk County. A small part of the city extends into Warren County. It was incorporated on September 22, 1851, as Fort Des Moines, ...

, and Burien. SR 509 is part of the National Highway System and is a

limited-access highway A limited-access road, known by various terms worldwide, including limited-access highway, dual-carriageway, expressway, limited access freeway, and partial controlled access highway, is a highway or arterial road for high-speed traffic which ...

near the

Port of Tacoma The Port of Tacoma is an independent seaport located in Tacoma, Washington. The port was created by a vote of Pierce County citizens on November 5, 1918. The ''Edmore'' was the first ship to call at the port in 1921. The port's marine cargo opera ...

and from Burien to its northern terminus in Seattle. Prior to the 1964 highway renumbering, the highway was part of Secondary State Highway 1V (SSH 1V) from Tacoma to Des Moines and SSH 1K from Des Moines to Seattle. SR 509 was re-aligned onto the Burien Freeway in 1968 and the Port of Tacoma bypass in 1997, coinciding with the opening of its interchange with I-705 and the

cable-stayed A cable-stayed bridge has one or more ''towers'' (or ''pylons''), from which cables support the bridge deck. A distinctive feature are the cables or stays, which run directly from the tower to the deck, normally forming a fan-like pattern ...

21st Street Bridge. A freeway extension of SR 509 within the city of SeaTac, connecting the Burien Freeway to

I-5 Interstate 5 (I-5) is the main north–south Interstate Highway on the West Coast of the United States, running largely parallel to the Pacific coast of the contiguous U.S. from Mexico to Canada. It travels through the states of Californi ...

, is planned to be completed by 2028.

Route description

SR 509 begins as South 21st Street at a

single-point urban interchange A single-point urban interchange (SPUI, or ), also called a single-point interchange (SPI) or single-point diamond interchange (SPDI), is a type of highway interchange. The design was created in order to help move large volumes of traffic thro ...

with I-705 in downtown Tacoma in Pierce County, providing access to the Tacoma campus of the

University of Washington The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington. Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seattle a ...

and the

Tacoma Link The T Line, formerly known as Tacoma Link, is a light rail line in Tacoma, Washington, part of the Link light rail system operated by Sound Transit. It travels between Tacoma Dome Station and Downtown Tacoma, serving six stations. The li ...

light rail line on Pacific Avenue. The highway travels east over the

Thea Foss Waterway The Thea Foss Waterway, formerly the City Waterway, is a north–south inlet of Commencement Bay separating downtown Tacoma, Washington, from the Port of Tacoma. History The City Waterway was created in 1902 through a dredging operation proposed ...

on the

21st Street Bridge into the

as a four-lane

, intersecting Portland Avenue in a half-

diamond interchange A diamond interchange is a common type of road junction, used where a controlled-access highway crosses a minor road. Design The freeway itself is grade-separated from the minor road, one crossing the other over a bridge. Approaching the ...

before crossing the

Puyallup River The Puyallup River ( ) is a river in the U.S. state of Washington (state), 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 ...

. SR 509 continues east, parallel to a City of Tacoma rail line through a

partial cloverleaf interchange A partial cloverleaf interchange or parclo is a modification of a cloverleaf interchange. The design has been well received, and has since become one of the most popular freeway-to-arterial interchange designs in North America. It has also bee ...

with Port of Tacoma Road before the divided highway ends at Taylor Way. The highway turns northwest along the Hylebos Waterway as Marine View Drive through the neighborhood of Northeast Tacoma towards Browns Point. SR 509 passes through Dash Point and its

state park State parks are parks or other protected areas managed at the sub-national level within those nations which use "state" as a political subdivision. State parks are typically established by a state to preserve a location on account of its natural ...

along the

into

and the city of

. The highway travels east as Dash Point Road through Federal Way past Decatur and

high school A secondary school describes an institution that provides secondary education and also usually includes the building where this takes place. Some secondary schools provide both '' lower secondary education'' (ages 11 to 14) and ''upper seconda ...

s before a junction with SR 99 west of

. The

concurrent Concurrent means happening at the same time. Concurrency, concurrent, or concurrence may refer to: Law * Concurrence, in jurisprudence, the need to prove both ''actus reus'' and ''mens rea'' * Concurring opinion (also called a "concurrence"), a ...

SR 99 and SR 509 travel north as the Pacific Highway past

Highline Community College Highline College is a public community college in Des Moines, Washington. Highline was founded in 1961 as the first community college in King County, Washington. The main campus covers . , there were approximately 17,000 students and 350,000 alu ...

to an intersection with SR 516 in 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 ...

. SR 509 turns west to form a concurrency with SR 516, heading past

Mount Rainier High School Mount Rainier High School is a secondary school in Des Moines, Washington, United States; named for Mount Rainier which can be seen quite well from the school on a clear day. Mount Rainier serves approximately 1700 students and has been active sinc ...

and into

, where SR 516 ends. SR 509 continues north onto Marine View Drive through the city of Normandy Park and into SeaTac. The highway turns southeast onto Ambaum Boulevard and

Des Moines Memorial Drive Des Moines Memorial Drive, also known locally as the Living Road of Remembrance, is a road in southern King County, Washington noted for its large numbers of American Elm trees planted as a memorial to soldiers killed in World War I. Route descript ...

to a

trumpet interchange In the field of road transport, an interchange (American English) or a grade-separated junction (British English) is a road junction that uses grade separations to allow for the movement of traffic between two or more roadways or highways, using ...

, the southern terminus of a limited-access

freeway A controlled-access highway is a type of highway that has been designed for high-speed vehicular traffic, with all traffic flow—ingress and egress—regulated. Common English terms are freeway, motorway and expressway. Other similar terms ...

section of SR 509. The four-lane freeway travels west of

through a closed half-diamond interchange with South 176th Street and a partial cloverleaf interchange with South 160th Street before entering the city of Burien. SR 509 passes

Highline High School Highline High School is a public high school in Burien, Washington, United States, located about 3.5 miles from Seattle–Tacoma International Airport. Highline High School, the flagship high school of the Highline Public Schools district, opene ...

before reaching a partial cloverleaf interchange with Southwest 148th Street and the western terminus of SR 518. The freeway continues north into the

West Seattle West Seattle is a conglomeration of neighborhoods in Seattle, Washington, United States. It comprises two of the thirteen districts, Delridge and Southwest, and encompasses all of Seattle west of the Duwamish River. It was incorporated as an i ...

neighborhood of

and intersects South 128th Street in a diamond interchange and South 112th Street in a half-diamond interchange. SR 509 enters the

Industrial District Industrial district concept was initially used by Alfred Marshall to describe some aspects of the industrial organisation of nations. Industrial district (ID) is a place where workers and firms, specialised in a main industry and auxiliary indu ...

of Seattle and heads through an interchange with Cloverdale Street and Myers Way before ending at a partial cloverleaf interchange with SR 99 south of the

First Avenue South Bridge The First Avenue South Bridge is a pair of double-leaf bascule bridges built between 1956 and 1998 that carry State Route 99 over the Duwamish River