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Signed County Route J4 and un-built California State Route 239

This past Fourth of July Weekend I drove most of Signed County Route J4 from California State Route 4 southeast towards Interstate 5.  J4 is a unique County Route which incorporates the corridor of un-built California State Route 239 in addition to small portions of the original alignments of US 48 and Lincoln Highway.


The route of J4 is signed from CA 4 in Contra Costa County southeast through Alameda County and San Joaquin County to Signed County Route J3 east of Banta.  J4 is a somewhat moderate length Signed County Route at 27.99 miles which was designated in 1960 according to CAhighways.org.

CAhighways.org on County Route J4

Between CA 4 southeast to I-205 in Tracy the route of J4 is along the planned corridor of CA 239.  Before the 1964 State Highway Renumbering the planned route of CA 239 was added to the State Highway System as a extension of Legislative Route Number 110 west from LRN 5 (US 50) to LRN 75 (CA 4) in 1959.

CAhighways.org on LRN 110

The extension of the planned route of LRN 110 to LRN 75 can be first seen on the 1960 State Highway Map.

1960 State Highway Map

As noted above the portion of LRN 110 from CA 4 to I-205 was swapped to CA 239 during the 1964 State Highway Renumbering.  This change can be seen on the 1964 State Highway Map.

1964 State Highway Map

According to CAhighways.org the planned route of CA 239 seems to still have traction as far as potential for being built in the future.  The planned route of CA 239 was incorporated into the failed plans for the Mid-State Tollway between Sunol and Vacaville.  In the recent two decades the planned route of CA 239 has had localized political support to be built as a freeway next to Byron Highway.

CAhighways.org on CA 239 

My approach to J4 south was from CA 4 east on Byron Highway in Contra Costa Highway.  CA 4 is briefly signed on the Byron Highway for about a quarter mile south of Marsh Creek Lane.  CA 4 continues east towards Stockton at Post Mile CC 44.369 whereas J4 begins heading southward on Byron Highway.  J4 oddly isn't signed with a reassurance shield from CA 4.








J4 south of CA 4 quickly enters the community of Byron on Byron Highway.





J4 southbound is fairly well signed with reassurance shields.  This shield below I barely captured entering Byron displays "Contra Costa" in the crest.


At Holway Drive J4 south cuts left to stay on Byron Highway and avoid a crossing of the Union Pacific tracks.


On the opposite side of the Union Pacific railroad tracks is a historic marker for the community of Bryon alongside an older Southern Pacific Railroad car.   Byron was founded in 1878 as a siding of the San Pablo and Tulare Railroad by the Central Pacific Railroad.  The San Pablo and Tulare Railroad was a line routed between Martinez to Los Banos which remains in service in modern times.  The Central Pacific Railroad as a whole became an operating subsidiary of the Southern Pacific Railroad in 1885.




J4 in Byron Highway in downtown Byron is routed east of the Union Pacific Railroad tracks.  One of the warehouse buildings has a mural of Byron as it was in 1878.



J4 southbound continues on Byron Highway towards the Alameda County Line.  At Byron Hot Springs Road there is signed access for Byron Airport.





J4 southbound crosses over to the western flank of the Union Pacific tracks and enters Alameda County just beyond the California Aqueduct.









J4 southbound is only in Alameda County for approximately a mile before it enters San Joaquin County on Byron Highway.


J4 southbound on Byron Highway enters the planned community of Mountain House which is presently only partially completed.  J4/Bryon Highway briefly expands to four-lanes but the traffic count alone illustrates the need (at least I thought so) for CA 239 to actually be built.  The bridge in the last photo below is Central Parkway and presently doesn't connect anywhere west of J4.





Mountain House takes it's name from a Gold Rush era stopover that was located roughly in the same area as the modern community.  The original Mountain House was founded in 1849 by Thomas Goodall for travelers heading from San Francisco Bay east over Altamont Pass towards the mines of the Sierra Nevada Range.  Mountain House grew into a small community but it heavily declined by the 20th Century into a ghost town.  The last remaining buildings from the original Mountain House were apparently demolished in the 1940s.  The modern community of Mountain House was named by San Joaquin County in late 1994.  Mountain House Parkway is one of the major roadways in the community and connects J4 southward towards I-205.


J4 southbound on Byron Highway continues south to Grant Line Road.  At West Grant Line Road J4 southbound briefly picks up the original alignment of the Lincoln Highway, US 48 and even early US 50.








J4 southbound splits off Byron Highway at East Grant Line Road.  US 48, US 50 and the Lincoln Highway continued south on Byron Highway into Tracy.



Upon crossing the Union Pacific tracks J4 southbound enters the City of Tracy on East Grant Line Road.



J4 south meets I-205 in Tracy along East Grant Line Road.





My intent on my drive on J4 was to only cover the un-built CA 239 portion between CA 4 and I-205.  That being the case I jumped on I-205 eastbound but immediately found the traffic to be a disaster.  That being the case I rejoined J4 south on East Grant Line Road via Tracy Boulevard which is a block east of the junction with CR J2 on Corral Hollow Road.


J4 south on East Grant Line Road crosses a set of railroad tracks and exits the City of Tracy.




J4 south on East Grant Line Road enters the community of Banta and crosses a set of railroad tracks where it again picks up the early Lincoln Highway alignment at G Street.




The Lincoln Highway eastbound traversed Banta originally by way of F Street, 7th Street and G Street to East Grant Line Road.  Banta was a siding of the First Transcontinental Railroad built by the Central Pacfic.  The community of Banta still has some structures dating back to it's heyday such as the 1879 Banta Inn.






East of G Street in Banta the route of J4 south on East Grant Line Road is co-signed as the Historic Lincoln Highway to I-205 Business.





Back in March of this year I tracked the early alignments of the Lincoln Highway, US 48 and US 50 in San Joaquin County.  Said blog can be found on the link below.

Hunting the early Lincoln Highway, US 48 and US 50 from French Camp west over Altamont Pass


J4 south traverses the roundabout at I-205 Business onto Kasson Road.  Via Kasson Road J4 south reaches I-5 where I turned south.






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