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County Route Shield

San Diego
County Sign Route S21

[Click here for a key to the symbols used. Some county routes were constructed with federal funds. These routes are indicated as FAP (Federal Aid Primary), FAU (Federal Aid Urban), or FAS (Federal Aid Secondary). If no funding source is shown, no federal funds were used. Note that while some segments seem to have the same attributes, they may differ in the county-local road number assigned to the segment, or in the Caltrans Map Sheet number.]

Routing Routing

  1. Cty Rte S21 / Old U.S. 101Genesee Avenue in San Diego from I-5 to N Torrey Pines Road (FAU, 0.80 mi)

  2. US Highway Shield Torrey Pines Road from Genesee Avenue to the Del Mar city limits (FAU, 3.98 mi)

  3. US Highway Shield Camino Del Mar in Del Mar from the Del Mar city limits to Jimmy Durante Blvd (FAU, 1.84 mi)

  4. US Highway Shield Camino Del Mar in Del Mar from Jimmy Durante Blvd to the Del Mar city limits (1.00 mi)

  5. US Highway Shield Old Highway 101 / Coast Highway 101 from the Del Mar city limits to the Carlsbad city limits (FAU, 8.10 mi)

    Status Status

    In November 2020, it was reported that Carlsbad Boulevard, the nearly seven-mile stretch of road also known as Old Highway 101 through Carlsbad, is about to get a third designation — U.S. Bicycle Route 95. The recognition would make Carlsbad Boulevard part of a national network of routes intended to facilitate interstate travel by bicycle on roads and highways identified as suitable for cycling. Carlsbad will be the last city in San Diego County to approve the designation. About 75 percent of the 1,000-mile route has been established from the California-Oregon border to the U.S. border with Mexico. Eventually, plans call for U.S. Bicycle Route 95 to extend to the Canadian border. East-West routes in the works include U.S. Bicycle Route 50 from San Francisco through South Lake Tahoe and on through Nevada and Utah, and Bicycle Route 66, which goes from Los Angeles through parts of Arizona and New Mexico. The American Association of State Highways and Transportation Officials created the U.S. Bicycle Route System in the early 1980s. So far there are designated bicycle routes in 24 states, used for cross-country travel, regional touring and commuting. Cities that agree to the designation are not required to take any additional action. No additional route markings, such as signs or bike lane markings, are required. More information on the U.S. Bicycle Route system may be found at the Adventure Cycling Association, Caltrans
    (Source: San Diego Union Tribune, 11/16/2020)

  6. US Highway Shield Carlsbad Blvd in Carlsbad from the Carlsbad city limits to the Oceanside city limits (FAU, 6.17 mi)

  7. US Highway Shield Coast Highway (formerly Hill Street) in Oceanside from the Oceanside city limits to I-5 (FAU, 2.85 mi)

History and Signage Information History and Signage Information

US Highway Shield This route was defined in 1968. Portions of this route are the former routing of US 101. Portions are the former Carlsbad Freeway, built between 1950 and 1953. specifically, the portion between La Costa and Palomar Airport Road. There was also a Business US 101 in this area.

Status Status

Some of the S-21 shields along old US 101 have been painted over with the California Poppy.

Rte S21 PostmileIn September 2009, it was reported that the Encinas Creek bridge was to be replaced in January 2010. Built in 1913, the Encinas Creek Bridge handles southbound traffic along Carlsbad Boulevard and is located about a half mile south of the Palomar Airport Road intersection. The bridge has low, concrete railings and a graceful, arched look. The bridge's exposed reinforcing bars have become "heavily corroded," and one of its two lanes ---- the western one ---- was shut down more than a year ago after the bridge failed a state Department of Transportation safety inspection. Plans call for the bridge to be replaced with a span that's 26 feet narrower, but 15 feet longer and two feet higher. The new span will be built off-site and trucked to the area to reduce the amount of time that Carlsbad Boulevard will be closed.
[Based on an article in the North County Times, "CARLSBAD: City to take out Encinas Creek bridge starting in January", 2009-08-31]

Business Route Shield Total mileage: 24.74 mi. At one time, the entire route was designated as Business Route 5; presently, only the old Highway 101 portion is Business Route 5. There are a few postmiles dating from the post-1964 renumbering showing the route as Route 5 (from when US 101 had been renumbered as Future I-5, but I-5 was still under-construction. The picture to the right was posted on AAroads by Kniwt.

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Acronyms and Explanations:

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© 1996-2020 Daniel P. Faigin.
Maintained by: Daniel P. Faigin <>.