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Post 1964 Legislative Route 239

Click here for a key to the symbols used. An explanation of acronyms may be found at the bottom of the page.

Routing Routing

Rte 239 (Unconst)FromRoute 580 west of Tracy to Route 4 near Brentwood.

Post 1964 Signage History Post 1964 Signage History

This route remains as defined in 1963. The traversable route is Mountain House Road and Byron Highway. Caltrans has no plans to adopt this route.

Pre 1964 Signage History Pre 1964 Signage History

This route was part of proposed LRN 110, defined in 1959. It was unsigned and unconstructed, although it appears to follow the route of Contra Costa/Alameda/San Joaquin County Sign Route J4.

Status Status

This routing is unconstructed. The traversable local routing is along Mountain House Road, and Byron Highway, as well as Vasco Road and Walnut Blvd. These existing roads are substandard for incorporation into the state system.

This route was originally planned to be a portion of the Mid-State Tollway between Sunol and Vacaville. The tollway was a proposal that would start off of I-680 near Sunol, cross I-580 west of Livermore (roughly along the alignment of the Livermore Bypass), and then will extend north to Route 4 near Antioch. A spur will come off the tollway near Brentwood and run SE to the junction of I-580 and I-205. The tollway could be designated Route 84, since it roughly follows the built and unbuilt portions of the route and the spur could be designated Route 239, since it follows the general routing for that unbuilt highway. The tollway was originally supposed to extend to I-80 between Vacaville and Dixon with a spur connecting with I-505 at the 80/505 junction, but that portion was killed due to the need for high-level crossings (150') of the San Joaquin and Sacramento Rivers plus environmental issues.

Note: For additional information on the Mid-State Tollway, see Route 84.

Scott Parker noted on AAroads that the tollway would have utilized the path of the oft-considered Route 239, Route 4 between Byron and Antioch, the Antioch (Route 160) bridge, and diverged from Route 160 north of there to cross the Sacramento River. It would have had terminating "splits" at both ends; a Route 84-based branch along Vasco Road, passing between Livermore and Pleasanton, and terminating at the Route 84 interchange with I-680 was to be a SW branch, while the main trunk, after crossing the Sacramento River, would have headed toward Elmira, where it would split into two branches, one intersecting I-505 about a mile or two north of I-80 (after crossing the latter freeway) and the other heading toward Dixon and the I-80/Route 113 freeway interchange between Dixon and Davis -- the Route 113 freeway would have been its functional extension. The toll road idea, formulated in the late '80's and early '90's, would have required a doubling of the Antioch Bridge as well as a 4-lane high-level bridge (likely cable-stayed) across the Sacramento River north of there. Even in 1992, the cost for doing the full project was projected at well over $2 billion; with the center section along Route 4 remaining a free facility (the present Antioch Bridge toll facility would have marked the southern end of the northern toll section). The Route 84 branch was itself mired in controversy; in the '90's the development of the Brentwood area as an "overflow" housing region for Silicon Valley employment was in its initial stages; deploying a toll road to serve that commute traffic was seen as gratuitous money-grubbing and that a conventional freeway would be more appropriate. But by 1998 the entire project was functionally scrapped because of the enormous cost; projected toll revenue was far too meager to even cover the initial construction -- likely due to the myriad opportunities for shunpiking as well as the perception that the northern section had limited commuter value and what revenue would accrue would come from commercial usage -- the most likely candidates to avoid the tolled facility!
(Source: AARoads "Re: I-5 West Side Freeway", 12/29/2019)

There is also an effort by Rep. Pombo to build a freeway along the Route 239 corridor. This freeway would would run along the path of the two-lane Byron Highway from the western end of Tracy northwest to Brentwood. There, it would connect with the Route 4 bypass currently scheduled for construction. Brentwood political leaders have been pushing for the new freeway to provide the city with a thruway to I-5, I-580, and I-205. The plan is to attract white-collar and industrial businesses and transform the city from a bedroom community to a job center. The new freeway proposal also will give Tracy commuters a connection to the north, and an alternative commute route to the East Bay. An article in the East Bay Express notes that the arrival of the federal funds for the Route 239 project also happens to coincide with a multimillion-dollar land deal currently underway with members of Pombo's family.

The SAFETEA-LU act, enacted in August 2005 as the reauthorization of TEA-21, provided the following expenditures on or near this route:

Interregional Route Interregional Route

[SHC 164.19] Entire route. It is believed this designation will provide increased funding. Designated by SB 802, Chapter 598, 9/2003.

Other WWW Links Other WWW Links

Statistics Statistics

Overall statistics for Route 239:

Freeway Freeway

[SHC 253.1] Entire route.

Scenic Route Scenic Route

[SHC 263.1] Entire route.

Pre-1964 Legislative Route Pre-1964 Legislative Route

In 1957, Chapter 23 defined LRN 239 as “a point on [LRN 56] near Daly City to a point on [LRN 2] near San Jose on a route to be selected by the California Highway Commission, which route may include all or portions of any existing state highway route or routes”. The urgency clause noted this was related to a circumferential freeway around San Francisco Bay.

In 1961, Chapter 1146 rewrote the routing as “the junction of [LRN 68] and [LRN 69] in San Jose to [LRN 56] near Daly City”.

This route is part of I-880 between the US 101/I-880 junction to the I-880/I-280 junction, and is I-280 between from I-880/I-280 N to LRN 56 (Route 1) near Daly City. Between San Bruno and Daly City, the route appears to duplicate LRN 237 (which may be the old surface street routing). Note that the I-280 route includes a portion of LRN 2 between old surface US 101 in Daly City and freeway US 101.

Acronyms and Explanations:

Back Arrow Route 238 Forward Arrow Route 240

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