|Length:||1,381.29 mi (2,222.97 km)|
|Existed:||1957 – present|
|South end:||Fed. 1 at Mexican border in San Diego, CA|
| I-8 in San Diego, CA
I-10 in Los Angeles, CA
I-580 / I-205 near Tracy, CA
I-80 in Sacramento, CA
I-505 in Dunnigan, CA
I-105 in Eugene, OR
I-84 in Portland, OR
I-705 in Tacoma, WA
I-90 in Seattle, WA
|North end:||BC 99 at Canadian border in Blaine, WA|
Interstate 5 (I-5) is the main Interstate Highway on the West Coast of the United States, running largely parallel to the Pacific Ocean and U.S. Highway 101 from Mexico to Canada (California to Washington). It serves some of the largest cities on the U.S. West Coast, including Seattle, Portland, Sacramento, Los Angeles, and San Diego, and also links the capital cities of Washington (Olympia), Oregon (Salem), and California (Sacramento) together. The highway's southern terminus is the Mexico – United States border and its northern terminus is the Canada – United States border; it is the only Interstate highway to touch the U.S. borders with both Canada and Mexico. Upon crossing the Mexican border at its southern terminus, Interstate 5 continues to Tijuana, Baja California as Mexico Federal Highway 1. Upon crossing the Canadian border at its northern terminus, it continues to Vancouver as British Columbia Highway 99.
Interstate 5 links to control cities in California (San Diego, Santa Ana, Los Angeles, Sacramento, Redding, Mount Shasta, Weed, and Yreka), Oregon (Ashland, Medford, Grants Pass, Roseburg, Eugene, Salem, and Portland), and Washington (Tacoma, Seattle, Everett, Mount Vernon, and Bellingham). North of Seattle, the control city is Vancouver, British Columbia; it is signed as "Vancouver B.C." in order to avoid confusion with Vancouver, Washington.
One notable control city that Interstate 5 does not directly reach is San Francisco, which is about 80 miles (130 km) west of the highway. To the south, in the Tracy area, Interstate 580 splits from I-5 towards San Francisco, while to the north, near Vacaville, Interstate 505 cuts south to Interstate 80, which serves that city. That routing, via I-580, I-80, and I-505, was planned originally as Interstate 5W.
Route description 
The most southerly point of Interstate 5 is at the United States-Mexico border at the San Ysidro border crossing, one of the busiest in the world. Beginning at the border in San Ysidro, which is part of the city of San Diego, as the John J. Montgomery Freeway, I-5 goes through the suburbs of National City and Chula Vista before reaching downtown San Diego. It then parallels the Pacific coastline, going through the northern suburbs of San Diego, bisecting the University of California, San Diego campus, and passing the I-805 merge, before passing through the 28 miles (45 km) of Marine Corps Base Camp Pendleton in northern San Diego County. Here I-5 is also known as the San Diego Freeway.
At Dana Point, I-5 turns inland and heads due north through Mission Viejo to the El Toro Y interchange in southeastern Irvine. I-5 becomes the Santa Ana Freeway as it runs southeast to northwest, passing through major cities and suburbs in Orange and Southern Los Angeles counties. Southern Californians refer to it as "the 5 Freeway" or as the Santa Ana Freeway in the Los Angeles area. From this point, the San Diego Freeway continues northward as I-405.
When the freeway reaches the East Los Angeles Interchange one mile (1.6 km) east of downtown Los Angeles, I-5 becomes the Golden State Freeway. The route continues through the San Fernando Valley and then crosses the Newhall Pass through the Santa Susana Mountains into the Santa Clarita Valley. For about a four-mile (6 km) stretch between Santa Clarita Valley and the Pyramid Lake, the northbound and southbound lanes separate and cross sides, with the southbound lanes running to the east of the northbound ones. At that point, the Golden State Freeway rises sharply to the north through the Grapevine to eventually reach the second-highest point of its entire length, the Tejon Pass (elevation 4,183 ft (1,275 m)). through the Tehachapi Mountains. Path 26 power lines generally follow the freeway along this stretch. The freeway then descends sharply for 12 miles (19 km) at Tejon Pass to around 1,600 feet (490 m) at Grapevine near the southernmost point of the San Joaquin Valley, approximately 30 mi (48 km) south of Bakersfield and 4 mi (6.4 km) south from where State Route 99 splits away from it in Wheeler Ridge.
From Highway 99 to south of Tracy, I-5 skirts along the far more remote western edge of the great Central Valley, and thus here is removed from population centers such as Bakersfield and Fresno; other state highways provide these connections. Interstate 580 splits off from I-5 at a point south of Tracy, providing a loop-route connection to the San Francisco Bay Area. After passing Tracy, I-5 heads north through Stockton and Sacramento before turning west to Woodland. At Woodland, the interstate heads northwest again towards Dunnigan, where it converges with Interstate 505.
From Dunnigan, I-5 skirts north along the western edge of the Sacramento Valley to Red Bluff. I-5 then enters the Shasta Cascade region, passing through Redding and Shasta Lake before climbing up to near the foot of Mount Shasta. The interstate then travels to Weed and Yreka before reaching the Oregon border.
About 3 mi (4.8 km) north of the California border, the highway crosses 4,310 feet (1,310 m) Siskiyou Summit, the highest point on I-5, and then drops down into the Rogue Valley through Oregon's southern mountains and towns such as Ashland, Medford and Grants Pass. Turning north across three passes to the Umpqua Valley and through Roseburg, the mountains tend to turn into hills, and as it reaches Cottage Grove, the road enters the Willamette River Valley. At Eugene the highway intersects Interstate 105, a short spur route into Downtown Eugene. Some city highways intersect on I-5 in the Eugene Metro. The interstate then heads almost due north, skirting Albany and Corvallis, passing through Salem, and crossing through Woodburn. There were plans to build a spur, called Interstate 305, into Salem. I-5 covers 308 miles (496 km) in Oregon.
Just north of Salem, between mile marks 259 and 260 just short of mile mark 260, signs in the median and on both shoulders marks the place where the 45th parallel crosses I-5. It reads "45th Parallel half way between the Equator and the North Pole".
The highway then tracks a little to the northeast, and Interstate 205 splits off south of the Portland metro area. From here I-5 passes through Tualatin and Tigard along former U.S. Route 99W before hitting the southern terminus of I-405 and the Marquam Bridge. Also planned was a spur in Portland off I-405, called Interstate 505, but it was never built and has been removed from city plans. A stub of I-505 exists as a long exit ramp to U.S. Route 30.
After crossing the Willamette River on the Marquam Bridge, I-5 has junctions at the western end of Interstate 84 and the northern end of I-405. It then continues through the northern parts of the city of Portland, and crosses into Washington via the Interstate Bridge.
The highway begins in Washington over the Columbia River and drops down into the city of Vancouver. About seven miles (11 km) into the state, it reaches the northern terminus of I-205, which is on the eastern edge of the Portland-Vancouver metropolitan area. It then tracks north by northwest to Kelso and Longview, at which point it ceases paralleling a large bend of the Columbia. Continuing north through the Willapa Hills, the freeway eventually reaches Olympia, where it bends sharply east, after that it goes through Joint Base Lewis-McChord (formerly Fort Lewis and McChord AFB), then finally Tacoma where it bends sharply north again to reach Seattle. The Ship Canal Bridge carries it over Portage Bay in Seattle. The freeway makes its way out of the Seattle/Tacoma/Everett metro area, crosses the floodplains of three rivers, through the Skagit Valley and the Mount Vernon-Burlington Metropolitan Area to the northern city of Bellingham to arrive at the Peace Arch Canadian border crossing between Blaine, Washington, and Surrey, British Columbia. Highway 99 continues northwest from the border into Vancouver, B.C. I-5 covers 277 miles (446 km) in Washington.
An extensive section of this highway (over 600 miles (970 km)), from approximately Stockton, California, to Portland, Oregon, follows very closely the track of the Siskiyou Trail. This trail was based on an ancient network of Native American footpaths connecting the Pacific Northwest with California's Central Valley. By the 1820s, trappers from the Hudson's Bay Company were the first non-Native Americans to use the route of today's I-5 to move between today's Washington State and California. During the second half of the 19th century, mule trains, stagecoaches, and the Central Pacific railroad also followed the route of the Siskiyou Trail. By the early 20th century, pioneering automobile roads were built along the path of the Siskiyou Trail, notably the Pacific Highway. The Pacific Highway ran from British Columbia to San Diego, California, and was the immediate predecessor of much of U.S. Route 99. The route of U.S. 99 was in turn used as a basis for much of the route of today's I-5.
A major deviation from the old U.S. 99 route is the Westside Freeway portion of I-5 in California's Central Valley. To provide a faster and more direct north-south route through the state, the decision was made to build a new freeway to the west and bypass Fresno, Bakersfield, and the rest of population centers in the area instead of upgrading the existing highway (which was re-designated as part of California State Route 99).
Major intersections 
- Interstate 805 (bypass) in southern San Diego [Exit 1A]
- Interstate 15 in San Diego (future; this freeway is currently signed as State Route 15) [Exit 13A]
- Interstate 8 in San Diego [Exit 20]
- Interstate 805 in northern San Diego [Exit 31]
- Interstate 405 at the so-called "El Toro Y" near Irvine, Calif. [Exit 94A]
- Interstate 605 in Santa Fe Springs, CA [Exit 123]
- Interstate 710 southeast of downtown Los Angeles
- Interstate 10 and U.S. Route 101 at the large East Los Angeles Interchange, east of downtown Los Angeles
- Interstate 110 southeast of Los Angeles
- Interstate 405 in Sylmar, Calif. [Exit 158]
- Interstate 210 in Sylmar [Exit 161A]
- Interstate 580 south of Tracy, Calif.
- Interstate 205 northeast of Tracy, Calif.
- Interstate 305 and U.S. Route 50 in Sacramento (I-305 hidden), called the Capital City Freeway. [Exit 518]
- Interstate 80 in Sacramento [Exit 522]
- Interstate 505 in Dunnigan, CA [Exit 552]
- U.S. Route 97 in Weed, California [Exit 747]
- Interstate 105 in Eugene, Ore. [Exits 194A and 194B]
- U.S. Route 20 in Albany, Oregon
- Interstate 205 in Tualatin, Ore. [Exit 288]
- Interstate 405 in Portland. Ore. [Exit 299B]
- Interstate 84 and U.S. Route 30 in Portland, Ore. [Exit 300B]
- Interstate 405 in Portland, Ore. [Exit 302C]
- Interstate 205 in Salmon Creek, Wash. [Exit 7]
- Interstate 705 in Tacoma, Wash. [Exit 133]
- Interstate 405 in Tukwila, WA [Exit 154A]
- Interstate 90 in Seattle, Wash. [Exit 164B]
- Interstate 405 (bypass) in Lynnwood, Wash. [Exit 182]
Auxiliary routes 
- San Diego, California - I-805
- Los Angeles, California - I-105
- Los Angeles and Orange County, California - I-605
- Los Angeles and Orange County, California - I-405
- Tracy, California - I-205
- Sacramento, California - I-305 (unsigned)
- Zamora, California - I-505
- Eugene, Oregon - I-105
- Portland, Oregon - I-405
- Portland, Oregon and Vancouver, Washington - I-205
- Tacoma, Washington - I-705
- Seattle, Washington - I-405
I-5 will have a complete set of auxiliary routes (105, 205, 305, 405, 505, 605, 705, 805, 905), with the completion of Interstate 905 in San Diego County. Currently, Interstate 80 and Interstate 90 are the only two interstates to have complete sets of auxiliary routes — by the numbers.
- "Route Log and Finder List: Table 1 - Interstate System". FHWA. Retrieved 2007-07-17.
- "Interstate 580 California". Interstate-Guide. Retrieved 2011-09-19.
- "Interstate 505 California". Interstate-Guide. Retrieved 2011-09-19.
- "Busiest border crossing". Interstate-guide.com. Retrieved 2011-11-27.
- "Museum of the Siskiyou Trail". Museumsiskiyoutrail.org. Retrieved 2011-11-27.
- Highways-Routes 1-8. California Highways. Accessed 09-19-2009
|Wikimedia Commons has media related to: Interstate 5|