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Interstate 405 Oregon

The tied arch, double deck Fremont Bridge (built in 1973) carries Interstate 405 over the Willamette River northwest of downtown Portland. The Fremont Bridge is the longest tied arch bridge in the world and supports 6,000 tons on its center span. This view of the bridge is seen from along the south bank of the river in the Northwest Industrial Area. Photo taken 08/27/06.


Interstate 405, known as the Stadium Freeway, is a short freeway looping around downtown Portland to the west of the Willamette River. The northern and southern terminus at Interstate 5 are on elevated stack interchanges located over the Willamette River. Interstate 405 appears to be cosigned with U.S. 26 on its southern half and is cosigned with U.S. 30 on its northern half.

Thomas Gill deciphers the U.S. 26 routing in this 02/11/03 email:

"You state that US 26 west is co-signed with 405 in the south, this is only partially true. Although the US 26 shield exists on over head signs going northbound, it doesn't exist southbound or on stand alone signs. Officially US 26 Flows over 405 onto city streets to OR-99W (Also not signed) and follows 99W south to the Ross Island Bridge with an interchange between OR-99W/US-26/OR-10/OR-43. The Reason 26 west is signed with 405 is because I-5 South doesn't have an easy way to connect with US 26 West, you must follow OR-43 south and use a loop back. Also 26 West is also signed with I-405 at the US-30 Interchange on the Fremont Bridge on the northern sections of 405 southbound. These signs should say TO:26 but they don't."

The U.S. 26 freeway, the Sunset Highway, heads northwest from Interstate 405 toward Seaside, where it meets U.S. 101. U.S. 25 used to continue north along the coast to Astoria, but that section is now exclusively U.S. 101 (as of 2004). An Interstate 505 was proposed westward along U.S. 30 from Interstate 405, but it was never built.


Construction on Interstate 405 (the Stadium Freeway) began in 1964, and the freeway opened in two stages: everything except the Fremont Bridge opened on February 25, 1969, and the Fremont Bridge opened on November 11, 1973. Interstate 405 was the single most expensive Interstate Highway construction project in Oregon, costing $121 million.

Highway Guides

Southern Terminus - Interstate 5 - southern Portland, Oregon
Perspective from Interstate 405 South
Now traveling southbound on Interstate 405 and eastbound on U.S. 26 (more or less), this is the final reassurance (pull through) sign for Interstate 405 south. After the U.S. 26 offramp (Exit 1C), Interstate 405 splits into north Interstate 5 to Interstate 84 east and south Interstate 5 to Salem and Eugene. Photo taken 08/27/06.
Southbound Interstate 405 reaches Exit 1C, Junction U.S. 26 east, 6th Avenue and Ross Island Bridge. After this interchange, Interstate 405 prepares to end at the southern interchange with Interstate 5. Photo taken 08/27/06.
Through this section of Interstate 405, the freeway remains below grade. At Exit 1C, Interstate 405 passes under Park Boulevard and a series of overpasses visible in the distance. Photo taken 08/27/06.
Use the left two lanes to continue south on Interstate 5, and the right lane becomes exit only for Interstate 5 north to Interstate 84/U.S. 30 east to follow the Columbia River to The Dalles, Eastern Oregon, and Boise. Photo taken 08/27/06.
Interstate 405 southbound widens out to four lanes, with the left two lanes preparing to transition to southbound Interstate 5 and the other two lanes transitioning to northbound Interstate 5 to Interstate 84 east. Photo taken 08/27/06.
Southbound Interstate 405 splits, with left lanes connecting to southbound Interstate 5 and right lanes connecting to northbound Interstate 5. There is no END shield for Interstate 405. Photo taken 08/27/06.
A fairly sharp ramp connects southbound Interstate 405 to southbound Interstate 5 (40 mph) as the ramp passes under Niato Parkway. Photo taken 08/27/06.
Southbound Interstate 405 merges onto Interstate 5 at the south end of the Marquam Bridge, which carries Interstate 5 over the Willamette River on a double-deck, cantilever span. Photo taken 08/27/06.
Perspective from Interstate 5 South
A ghost ramp is situated to the left of southbound Interstate 5 in Portland as the freeway approaches the second junction with Interstate 405. In addition, this exit connects Interstate 5 southbound to U.S. 26 westbound via Interstate 405 northbound. The ghost ramps on Interstate 5 on the Marquam Bridge were intended to connect to the never-built Mount Hood Freeway, which would have been a freeway alignment for U.S. 26 from that point through Gresham to the east (a small part of it was built southeast of Gresham). It was killed, along with Interstate 505, Interstate 305/Salem Parkway, and several planned freeway projects in Eugene as a result of Oregon's Freeway Revolt in the 1970s. There are also ramps at Interstate 405's northern end which now lead to Kerby Avenue, but the ramps were originally intended for a freeway into northeast Portland. Photo taken 08/27/06.
Interstate 5 southbound approaches the southern terminus of Interstate 405. Photo taken on the lower level of the Marquam Bridge crossing the Willamette River. Photo taken 08/27/06.
At the end of the Marquam Bridge is the interchange between Interstate 5, Interstate 405, and U.S. 26. This view shows the stack interchange as seen along southbound Interstate 5 at the end of the double decked section of the bridge. The ramp to Interstate 405 north and U.S. 26 west is a left exit, sweeping under Interstate 5 to connect directly with U.S. 26 and Interstate 405. Photo taken 08/27/06.
Perspective from Interstate 5 North
The first advance signage for Interstate 405 on northbound Interstate 5 is this overhead on the approach to Exit 298 (Corbett Avenue), Exit 299A (Junction U.S. 26 East/Ross Island Bridge), and Exit 299B (Junction Interstate 405 North and U.S. 26 West to Beaverton, Portland Zoo, and Hoyt Arboretum). Photo taken 08/27/06.
Interstate 5 follows the west bank of the Willamette River on the approach to downtown Portland and the split with Interstate 405. U.S. 26 and Oregon 43 interchange with the freeway at Exit 299A just south of the Exit 299B junction with Interstate 405 west. U.S. 26 crosses the Ross Island Bridge from Oregon 43 (MacAdam Avenue) east to Oregon 99E (McLoughlin Boulevard). Interstate 84 shields accompany Interstate 5 northbound signs for Exit 300. Photo taken by Chris Elbert (03/06/04).
Interstate 405 veers northwest from Interstate 5 northbound at Exit 299B. The downtown loop parallels U.S. 26 (Clay Street, Market Street, and Naito Parkway [formerly Front Ave]) between Interstate 5 and its travels along the Sunset Highway west from Portland to Beaverton. The central business district of Portland lies along the west banks of the Willamette River. Traffic destined for downtown should use Interstate 405 north Exits 1B or 1C. Photo taken 08/27/06.
Perspective from Interstate 405 North
The first exit along northbound Interstate 405 after the southern Interstate 5 interchange is Exit 1A, Niato Parkway. Upon departing Interstate 5 north, you exit onto the beginning of the old Harbor Freeway, which was another casualty of Oregon's Freeway revolt in the 1970s; most of its old routing is now Portland's Waterfront Park, but it used to connect to the Steel Bridge and carried U.S. 99W. The stub that remains (which you'd get on if you don't exit for Interstate 405) extends for about a half mile north, then turns to meet Naito Parkway. This is where U.S. 26's official routing turns off Naito to run through downtown Portland. Anyway, when Interstate 405 was begun the Harbor Freeway still existed, so Interstate 405 was partially tied into it at its southern end. Photo taken 08/27/06.
Northbound Interstate 405 follows the two right lanes over the Niato Parkway exit, while the two left lanes serve Niato Parkway (abandoned Harbor Freeway). Photo taken 08/27/06.
The interchange between Interstate 5, Interstate 405, Niato Parkway, U.S. 26, and city streets is rather complex. Several ramps approach the mainline of Interstate 405 as it steers through the complicated series of ramps and connectors. Photo taken 08/27/06.
The next exit along northbound Interstate 405 after the southern Interstate 5 interchange is Exit 1B, 4th Avenue, followed by Exit 1C, 6th Avenue. The Ocean Beaches sign for Exit 1D refers to the exit for westbound U.S. 26. Photo taken by Chris Elbert (04/24/05).
Northbound Interstate 405 reaches Exit 1D, Junction Westbound U.S. 26. This photo shows how far south the U.S. 30 reference is made; either U.S. 26 or U.S. 30 is generally shown on the overhead signage for pretty much the entire length of Interstate 405. Photo taken by Chris Elbert (04/24/05).
Northern Terminus - Interstate 5 - northern Portland, Oregon
Perspective from Interstate 405 North
Interstate 405 approaches the northern terminus. Signage is present for Interstate 5 north/U.S. 30 east on the lower level of the Fremont Bridge crossing the Willamette River. Photo taken 08/27/06.
Use Interstate 5 south to Interstate 84 (Banfield Freeway) eastbound to The Dalles. Photo taken by Chris Elbert (04/24/05).
Terminus of Interstate 405 at the U.S. 30 ramp before traffic merges with Interstate 5 at the end of the Fremont Bridge. Photos taken 08/27/06 and by Chris Elbert (04/24/05).
Northbound Interstate 405 reaches the offramp for Kerby Avenue as it prepares to leave the lower deck of the Fremont Bridge and rejoin Interstate 5. Photo taken 08/27/06.
The upper levels of the Fremont Bridge split off of Interstate 405, and the two remaining through lanes see daylight for the first time since entering the bridge. Photo taken 08/27/06.
A flyover ramp carries the two lanes of northbound Interstate 405 onto northbound Interstate 5. Photo taken 08/27/06.
Interstate 405 ends as it merges onto northbound Interstate 5 near Exit 303, Killingsworth Street. Continue north on Interstate 5 to Vancouver, Longview, Olympia, Tacoma, and Seattle. There is no END shield present for Interstate 405. Photo taken 08/27/06.
Perspective from Interstate 5 North
After the merge with traffic from Interstate 84/U.S. 30, northbound Interstate 5/westbound U.S. 30 reach Exit 302A, Broadway and Weidler Street to the Rose Quarter in downtown Portland. The next exit is the junction with Interstate 405 south and U.S. 30 west (Exit 302B). Photo taken 09/02/06.
Follow U.S. 30 west (via Exit 302B) to the N.W. Industrial Area. U.S. 30 plies along the Willamette River waterfront through industrial areas, warehouses, and ports. Photo taken 09/02/06.
Interstate 5 northbound at the Flint Avenue overpass one-quarter mile south of the Exit 302B departure for Interstate 405 & U.S. 30 westbound. U.S. 30 merges onto Interstate 5 north from Interstate 84 west at Exit 300. From there the US route travels north with Interstate 5 to Interstate 405 west across the Fremont Bridge. Photo taken 09/02/06.
The left two lanes continue north on Interstate 5 to Vancouver, Olympia, Tacoma, and Seattle. The right two lanes prepares to exit to Interstate 405 south and U.S. 30 west over the Fremont Bridge. Photo taken 09/02/06.
A high-speed stack interchange composes the junction between Interstate 5-405 and U.S. 30 at Exit 302B. The westbound control city of Interstate 405 is St. Helens for the U.S. 30 departure from Portland via St. Helens Road to the northwest. St. Helens lies along the Columbia River 30 miles northwest of the Portland urban loop. Interstate 5 meanwhile continues another five miles to junction U.S. 30 Bypass (Lombard Street). Photo taken 09/02/06.
Perspective from Interstate 5 South
This mileage sign found along southbound Interstate 5 provides the distance to the Interstate 405 and Interstate 84 interchanges in Portland. Photo taken Chris Elbert (04/24/05).
One mile north of the Interstate 5 junction with Interstate 405 & U.S. 30 (Exit 302B) at the Killingsworth Street overpass. Exit 303 leaves the freeway here for Alberta Street and Going Street west to Swan Island. Interstate 405 sees Beaverton as its southbound control city for the connection with U.S. 26 (Sunset Highway) west. Photo taken 08/27/06.
Follow U.S. 30 west to the Northwest Industrial Area. Use Interstate 405 south to U.S. 26 west to the Oregon Zoo and Hoyt Arboreteum. Photo taken 08/27/06.
Traffic from Going Street and Alberta Street merge onto Interstate 5 southbound to add an auxiliary lane between the Falling Street Pedestrian Bridge and junction Interstate 405 & U.S. 30 (Exit 302B). Interstate 5 narrows to four lanes through the Interstate 405 stack interchange. Photo taken 08/27/06.
Interstate 5 partitions into the southbound mainline for Interstate 84 & U.S. 30 east to The Dalles and Interstate 405 & U.S. 30 west for downtown Portland, St. Helens (via U.S. 30 west), and Beaverton (via U.S. 26 west). Interstate 405 & U.S. 30 cross the Willamette River between here and their split. Photo taken 08/27/06.
Perspective from Interstate 405 South
Interstate 405 in Oregon has one of the most beautiful termini in the Interstate Highway System. Immediately after splitting off of Interstate 5, Interstate 405 climbs onto an approach ramp that leads onto the massive, elegant Fremont Bridge over the Willamette River. The graceful structure is best seen on southbound Interstate 405 since southbound lanes ride on the top deck. Photo taken 08/27/06.
The superstructure of the tied arch Fremont Bridge comes into view as ramps from U.S. 30 west join Interstate 405 south. The freeway carries four southbound lanes across the main span. After the superstructure section, U.S. 30 debarks toward the Northwest Industrial Area, while Interstate 405 continues south into downtown Portland before rejoining Interstate 5. Photo taken 09/02/06.

Page Updated September 10, 2006.


State Oregon
Mileage 3.53
Cities Portland
Junctions Interstate 5
Source: December 31, 2015 Interstate Route Log and Finders List
I-405 Oregon Annual Average Daily Traffic
County MP Location AADT Composite
Multnomah 0.60 0.60 mile west of I-5 100,100
Multnomah 0.88 S.W. 4th Avenue Undercrossing 91,500
Multnomah 1.11 S.W. Broadway Undercrossing 79,100
Multnomah 1.18 S.W. Park Avenue Undercrossing 125,500
Multnomah 2.02 S.W. Yamhill Street Undercrossing 97,700
Multnomah 2.45 N.W. Glisan Street Undercrossing 92,440
Multnomah 2.65 N.W. Kearney Street Overcrossing 104,400
Multnomah 3.05 Fremont Bridge 110,600
Source: 2002 Traffic Volumes (ODOT)