Interstate 405 (I-405), also known as the Stadium Freeway No. 61, is a short north–south Interstate Highway in Portland, Oregon. It forms a loop that travels around the west side of Downtown Portland, between two junctions with I-5 on the Willamette River near the Marquam Bridge to the south and Fremont Bridge to the north.
The Stadium Freeway was envisioned in the 1940s and 1950s by the state government and was added to the Interstate Highway system in 1958. Construction began in 1963, utilizing a trench with extensive landscaping and frequent overpasses, and was the most expensive freeway project in state history at a cost of $121 million. Hundreds of buildings were demolished to make way for the freeway, which displaced approximately 1,100 households.
The southernmost section of I-405 opened on October 26, 1965, and was followed by extensions in 1966 and 1969. The final section, including the Fremont Bridge, opened in November 1973. Plans for a spur freeway, I-505, were cancelled in 1978 following public outcry; its interchange with I-405 was subsequently reused for a 1988 realignment of U.S. Route 30 (US 30), which runs concurrent with I-405 across the Fremont Bridge to I-5.
Route description
I-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 passing the end of the South Park Blocks. It begins a short concurrency with US 26.
US 26 splits from I-405 at an interchange north of Montgomery Street, traveling via the Vista Ridge Tunnels onto the Sunset Freeway towards 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 Glisan Street, the freeway becomes 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 cancelled 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 to Legacy Emanuel Hospital along the alignment of the cancelled Rose City Freeway.