Interstate 5 in California

Interstate 5, often called I-5, is a very important road that goes from the Mexican border all the way up to the Oregon border in California. It is the longest interstate highway in California, stretching about 797 miles. It connects many big cities, including San Diego, Santa Ana, Los Angeles, Stockton, Sacramento, and Redding.

This highway is part of a big system of roads called the Interstate Highway System that helps people travel across the United States. It runs close to the Pacific Coast and is the main way to get from the south to the north in California. Another important road, U.S. Route 101, also runs up the coast but stays closer to the ocean.

People in California often call I-5 simply "the 5." Different parts of the road have special names, like the John J. Montgomery Freeway, San Diego Freeway, Santa Ana Freeway, Golden State Freeway, and West Side Freeway. It is very busy and helps millions of people travel each day.

Route description

Interstate 5 (I-5) is a major highway that runs from the Mexican border all the way to the Oregon border, passing through California. It is the longest interstate in California, stretching over 796 miles.

Starting at the San Ysidro Port of Entry near San Diego, I-5 travels through many important cities and areas. It goes through San Diego, Los Angeles, the Central Valley, and Sacramento before reaching the Oregon state line near Yreka. Along the way, it connects many communities and serves as a key route for travel across the state. The highway is part of important transportation networks and offers scenic views, especially in areas like the Tejon Pass and the Cascade Region.

History

Historical naming

The part of this highway from Los Angeles to San Diego was also known as US 101 until 1964–1968. The stretch from Woodland to Red Bluff follows the old US 99W route.

In California, the former western branch of Interstate 5, connecting I-80 out of Vacaville to near Dunnigan, was renamed I-505. Interstate 580, running between I-5 and I-80, was once designated 5W; the part that runs through Sacramento was originally designated I-5E.

The term "Golden State Highway" was a popular name for US 99 through California, chosen in a public contest in 1927, but it was never officially adopted. Since I-5 was built, it has taken over the name "Golden State Freeway" from US 99 south of its southern end in Kern County.

Los Angeles area

The Golden State Freeway was first suggested by the California Highway Commission in 1953. Many people in East Los Angeles opposed it because it would remove homes and businesses from areas like Boyle Heights and Hollenbeck Heights. The proposal seemed to ignore the needs of the Mexican American community in Los Angeles. A group called the "Boyle–Hollenbeck Anti–Golden State Freeway Committee" formed to try to stop or change the freeway’s path. Despite this, the freeway was built.

When this part of the freeway was finished in 1956, a newspaper wrote that it had removed many homes in East Los Angeles. In 1958, a resident named Lomie Puckett tried to stop workers from taking her home by threatening them with a rifle. After several days, the home was taken away.

The part of the freeway between Orange County and Los Angeles was planned to have three lanes each way. Because so many people wanted to use it, the freeway was widened many times, especially in Orange County in the 1990s. More work was done in 2010 and 2023 to improve it further.

Newhall Pass

The original road went through the towns of Saugus and Newhall, and crossed Newhall Pass. In 1862, a narrow road called Beale's Cut was built there. In 1910, a tunnel called the Newhall Tunnel was built, but it was too narrow for trucks. In 1939, the tunnel was removed and the road was widened. By 1930, a new road was built to avoid Newhall Pass through Weldon and Gavin canyons, which is the route I-5 uses today.

Both roads were made into freeways. The Gavin Canyon route became I-5, and the Newhall Pass route became SR 14. The Newhall Pass interchange has collapsed twice during earthquakes, in 1971 and 1994. After the 1994 earthquake, it was renamed to honor a police officer who died when a bridge fell.

Ridge Route

The Ridge Route is the part of the highway between Castaic and Grapevine through Tejon Pass. It began in the early 1910s when a new route was needed to connect Los Angeles to the Central Valley. The first road was finished in 1915, but it was slow and winding. It was improved over the years, and in 1933, a new three-lane road called the Ridge Route Alternate was built. More changes were made over time, and by 1970, it became the modern Ridge Route we see today.

San Joaquin Valley

When the Interstate Highway System started in 1956, there was a debate about how to route I-5 through the San Joaquin Valley. One idea was to upgrade the Golden State Highway (US 99, later SR 99) to a freeway. The other idea was to build a new route called the West Side Freeway, which would bypass the towns and provide a faster path north and south. The West Side Freeway was chosen.

Building the West Side Freeway began in the early 1960s. The first part opened in 1967, the second in 1972, and the final part in 1979. At first, there were few businesses along the road, and travelers sometimes ran out of fuel. Over time, businesses grew up to serve travelers. There has been interest in making the Golden State Highway its own interstate, possibly I-7 or I-9.

I-5W and the San Francisco Bay Area

I-5’s main route from Los Angeles to Sacramento does not go through San Francisco, San Jose, Oakland, or the rest of the San Francisco Bay Area. Original plans included a loop called I-5W. This route now matches parts of I-580, I-80, and I-505. Most interstates with directional suffixes like I-5W were changed or removed, but I-5W is still sometimes mentioned.

Sacramento area

Interstate 5 in downtown Sacramento follows the Sacramento River, which made engineering challenging to keep the road dry. Local workers call this part the "Boat Section." In 1980, heavy rain flooded this area. Construction began in the 1960s and 1970s, with special drainage systems to protect the road. Major repairs were needed in 2008 after years of sand and silt buildup.

Redding to Oregon

In 1992, the last 13 miles of I-5 north of Lakehead were upgraded.

HOV lane expansion in Southern California

I-5 in north San Diego County is being expanded with new carpool lanes as part of the North Coast Corridor project. The carpool lane expansion from Lomas Santa Fe Drive to SR 78 opened in late 2023. In Orange County, carpool lanes opened in the mid-1990s and have been extended over the years. In Los Angeles County, carpool lanes have been added in stages, with the latest section set to open in 2026. Plans are also being studied to extend carpool lanes further in Orange County.

Exit list

Unsigned State Route 5S

There are two special roads in Los Angeles County that are part of Interstate 5 but do not have signs showing their names. Both of these roads are called Route 5S, which stands for "supplemental".

Colorado Street Freeway Extension (exit 142)

The Colorado Street Freeway Extension is a short road that was once part of State Route 134. It now connects to I-5 at exit 142/Colorado Street and has additional connections to Colorado Boulevard, Edenhurst Avenue, and San Fernando Road.

All exits along this road do not have numbers.

Newhall Pass truck route

There is a special route for trucks using I-5 through the Newhall Pass Interchange in Sylmar. This route has its own separate exits, starting from the I-210 interchange and going north past the SR 14 interchange.

All exits along this truck route do not have numbers.

Related routes

Interstate 5 in California has several connected highways that help drivers travel around big cities and other areas.

• I-105 connects to Los Angeles International Airport and heads east.
• I-205 loops around the top of Tracy.
• I-405 runs around the edges of Greater Los Angeles.
• I-505 links up north from Vacaville to near Dunnigan.
• I-605 travels from Seal Beach up to Duarte.
• I-805 circles around the San Diego area from near the Mexico–U.S. border.

There is also an unsigned highway, I-305, and a future highway planned to become I-905. Some older roads also follow parts of the old US 99 route.