A map of central Portland with I-405 highlighted in red
|Auxiliary route of I-5|
|Maintained by ODOT|
|Length||4.25 mi (6.84 km)|
|South end||in Portland|
| in Portland|
|North end||/ in Portland|
Interstate 405 (I-405, also known as the Stadium Freeway No. 61) is a short Interstate Highway in Portland, Oregon. It forms a loop that travels around Downtown Portland west of the Willamette River, between two junctions with I-5 at the Marquam Bridge and Fremont Bridge.
The freeway was constructed in the mid-1960s, utilizing a trench with extensive landscaping and frequent overpasses. Most of it opened on February 25, 1969, while the Fremont Bridge opened several years later in September 1973.
Interstate 405 begins at a three-way stack interchange with I-5 and Harbor Drive on the south side of Downtown Portland near the South Waterfront neighborhood. I-5 continues northeast from the interchange to the Marquam Bridge to East Portland and south towards South Portland, passing under the Ross Island Bridge. I-405 travels northwest along the foothills of the Southwest Hills, traveling around the urban campus of Portland State University and beginning a short concurrency with U.S. Route 26 (US 26).
US 26 splits from I-405 at an interchange north of Montgomery Street, traveling onto the Sunset Freeway bound for the western suburbs of Portland. I-405 then turns northeast and narrows to four lanes as it travels through the east edge of the Goose Hollow neighborhood, passing the Multnomah County Central Library, Lincoln High School, and Providence Park, home of several local soccer teams. The below-grade freeway is connected to the neighborhood and the western fringe of downtown by a series of ramps that lead to Salmon and Taylor streets. At Yamhill and Morrison streets, I-405 crosses under bridges carrying MAX Light Rail trains, which continues west towards Beaverton and east to Downtown Portland.
I-405 intersects Burnside Street and turns due north as it climbs out of the below-grade trench, running parallel to 15th and 16th avenues. After an interchange with Gilsan Street, the freeway become elevated and passes over cross-streets in the Pearl District, including those carrying the tracks of the Portland Streetcar's NS Line. A streetcar maintenance barn and railyard is located under the freeway between Marshall and Overton streets. At the northwest edge of Downtown Portland, I-405 intersects US 30, which continues northwest along a short freeway into the Northwest Industrial Area that was originally intended for the canceled I-505.
I-405 and US 30 become concurrent as they cross over the Willamette River on the eight-lane Fremont Bridge, a steel tied-arch bridge that carries southbound traffic on its upper deck and northbound traffic below. The double-decker freeway continues northeast over the Union Pacific Railroad's Albina railyard and Interstate Avenue, a part of Route 99W that also carries the MAX Yellow Line. The northern terminus of I-405 is at a stack interchange with I-5 in the Eliot neighborhood; US 30 continues southeasterly onto I-5 for a short distance before beginning a concurrency with I-84. A set of ramps continue northeast from the interchange along the alignment of the canceled Rose City Freeway, serving as a connector to Legacy Emanuel Hospital.
Highway planner Robert Moses was commissioned to design a freeway network for Portland in 1943, including what he envisioned to be a downtown loop that later formed the basis for Interstate 405. Construction of the Stadium Freeway began in 1964, after $25 million in condemnations and land acquisitions, and largely consisted of excavating a trench between two city blocks. The majority of Interstate 405, between Montgomery and Johnson streets, was opened to traffic on February 25, 1969, after two months of delay due to unfavorable weather. The freeway employed extensive use of retaining walls and overpasses to reduce disruption for cross-traffic. The loop was completed in September 1973 with the opening of the Fremont Bridge, linking I-405 to I-5 in North Portland. The 4.2-mile (6.8 km) I-405 and Fremont Bridge cost a total of $121 million to construct, making it the most expensive freeway project in Oregon on a per-mile basis. In August 2009, the entire route with the exception of the Fremont Bridge was completely repaved for the first time after it opened to traffic. The bridge itself was repaved in August 2011.
In 1998, Mayor Vera Katz proposed capping a portion of the freeway in Downtown Portland with buildings and parks. Similar proposals have been made by grassroots organizations since then, aiming to mitigate the effects of the freeway and create new development in the neighborhood. A short bridge, named Flanders Crossing, is planned to create a pedestrian and bicycle connection across I-405 between two sections of Northwest Flanders Street in Northwest Portland. The $6 million project was approved in 2016 and is planned to begin construction in 2020.
|-0.04||-0.064||--||south - Salem||Exit 299B on I-5|
|0.52||0.84||1A||South Waterfront - City Center||Northbound exit and southbound entrance|
|0.52||0.84||--||north to east - The Dalles, Seattle||Southbound exit and northbound entrance|
|0.89||1.43||1B||4th Avenue||Northbound exit and southbound entrance|
|1.03||1.66||1C||east / 6th Avenue - Ross Island Bridge||South end of US 26 concurrency|
|1.40||2.25||1D||12th Avenue||Northbound exit and southbound entrance|
|1.62||2.61||west - Beaverton||North end of US 26 concurrency|
|1.92||3.09||2A||Salmon Street - Providence Park||Northbound exit and southbound entrance|
|2.20||3.54||Burnside Street / Couch Street||Southbound exit and northbound entrance|
|3.08||4.96||3||west - Northwest Industrial Area, St. Helens||South end of US 30 concurrency|
|3.78||6.08||--||east (I-5 south) - The Dalles||North end of US 30 concurrency; northbound exit and southbound entrance|
|4.18||6.73||--||Kerby Avenue||Northbound exit and southbound entrance|
|4.21||6.78||--||north - Seattle||Exit 302B on I-5|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi|