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I-405  California (link)

72.15 miles [1note]; the 405 (San Diego Fwy) serves the San Fernando Valley, the beaches, and Orange County.

I-405 was approved as a chargeable interstate on Sept. 15, 1955. [3note] [4note] The first section of I-405 opened in 1957, signed as CA 7. The part west of I-605 was done before 1965; the newest section, near the southern junction with I-5, opened in 1969. [5note] [7note]

When the number for this route was being decided (in the 1950s), California suggested "Interstate 9." [3note]

See also:

  • I-405 (Dan Faigin)
  • 405: the Movie a digital independent short movie shot on location on I-405. Getting it to play on your computer might be like pulling teeth, and iFilm will want you to "register", but it's worth it.


I-405  Oregon (link)

3.53 miles [1note]; this is the Stadium Freeway, looping west of I-5 in Portland. It opened to traffic on Feb. 25, 1969. [11note] It contains an interchange intended for the cancelled I-505.

See also:


I-405  Washington (link)

30.30 miles [6note]; goes east of Lake Washington to serve suburbs of Seattle.

The idea for a bypass road is at least 60 years old. When the US 10 freeway (now I-90) from Seattle to Issaquah was built in 1940, designers put in a two-lane overpass where I-405 would eventually be built. The overpass sat unused for 14 years (this is not, however, anywhere close to a record.)

The portion of I-405 from NE 160th St. to what is now Sunset Blvd opened in stages from 1954 to 1957. It was originally called "Secondary State Hwy 2A" (SSH-2A) until 1964, when it became State Route 405. It was to have been posted US 99E, but by 1964 the 405 signs were replacing WA 1 signs. The section from I-90 to Kirkland was 4 lanes, as was the section between 112th and Sunset Blvd in the south end; the remainder was 2 lanes, undivided. [6note]

The southern end was upgraded by 1965, and the north end was connected to I-5 in 1968. The section in between 160th St. and Kirkland was widened to six lanes around 1971. [10note]

Severe congestion on Interstate 405 has triggered a dust-off of a 1960s proposal for an outer bypass called Route 605. The fate of this route is far from certain.

See also: I-405 (Paul Henry)


  1. Route Log and Finder List - Interstate Highways, FHWA, Oct. 31, 2002.
  2. Faigin, Daniel. "Interstate Highway Types and Interstate History." Web page: http://www.cahighways.org/itypes.html.
  3. "History of California's Interstate Routes." California Department of Transportation, November 1984.
  4. Brodsly, David. LA Freeway. Berkeley: University of California Press, 1971.
  5. Bozanich, Mark
  6. Cooper, Grant
  7. Sinden, Mark
  8. Oregon Department of Transportation. "A chronological history of ODOT: 1899 to 1993." http://www.odot.state.or.us/ssbpublic/bss/rmds/history/~chron.htm (12 March 2004)