The emergence of the automobile in the early 20th Century in California led to the 1909 First State Highway Bond Act which was approved by voters during 1910. The majority of the highways approved as part of the First State Highway Bond Act were largely well established routes of travel. One such highway was Legislative Route Number 4 ("LRN 4") which was defined as a highway from "Sacramento to Los Angeles."
During 1912 Indiana Businessman Carl G. Fisher conceptualized the Lincoln Highway as a major transcontinental Auto Trail. The Lincoln Highway was formally dedicated on October 31st, 1913 and would be aligned south from Sacramento southward towards Stockton via the existing highway corridor. From Galt the Lincoln Highway southwards followed existing LRN 4/Lower Sacramento Road through Woodbridge and Lodi onward into Stockton. The original alignment of the Lincoln Highway through Stockton followed; Pacific Avenue, Maple Street, El Dorado Street, Weber Avenue, Center Street and French Camp Parkway towards French Camp. This early alignment of the Lincoln Highway through Stockton can be seen on the Lincoln Highway Association's Official Map.
The planned route of LRN 4 can be seen on the on the 1917 California State Automobile Association Map. The planned route of LRN 4 (denoted as the red line) was conceived as a direct alignment from Galt to Lodi which would bypass Woodbridge. LRN 4 was planned to be realigned towards an eastern approach to Stockton via what is known Cherokee Road.
The September 1924 California Highways & Public Works details the issues presented by upgrading LRN 4/Lincoln Highway between Sacramento and Stockton. A segment of oil bound macadam surface extending thirteen miles southward from Sacramento laid by Sacramento County in 1910 is cited as a problematic area. This segment of the Lincoln Highway was transferred to the State Highway System as part of LRN 4 during July of 1915 and had become functionally obsolete due to increasing traffic. The macadam surface is described as being replaced by a twenty foot wide Portland Cement surface.
The below photo is a illuminated warning sign on the Lincoln Highway/LRN 4 denoted thirteen bridges were under construction between Sacramento and Stockton. This photo can be seen in the September 1924 California Highways & Public Works.
The January 1925 California Highways & Public Works notes that twelve new bridges along the Upper Stockton Road (Lincoln Highway and LRN 4) had been completed.
The April 1928 California Highways & Public Works cites the new entrance alignment of US 99/LRN 4 as being nearly completed. Contractors are cited to have encountered delays with completing grading due to wet weather.
The shift of LRN 4 onto Mariposa Road resulted in Division of Highways shifting US 99 out of French Camp and Lathrop (which appears to have been done without AASHO approval) on the new new direct highway to Manteca. The Division of Highways subsequently made a request to the AASHO during February 1929 to extend US 48 via LRN 5 to US 99/LRN 4 in Stockton. This proposed extension of US 48 would see it aligned over the new grade of LRN 5 from French Camp northward into Stockton. An additional southern spur of US 48 was proposed to connect with US 99/LRN 4 in Manteca The AASHO rejected the concept proposed by Division of Highways but offered an alternative which truncated US 48 from San Jose to Hayward and from French Camp to Mossdale. This alternative conceptualized US 101E and the US 99W/US 99E split from Stockton-Manteca. The truncation of US 48, creation of US 101E and creation of the US 99W/US 99E Stockton-Manteca split was approved in April of 1929 by the AASHO Executive Committee.
The November 1929 California Highways & Public Works notes a contract to construct two bridges over French Camp Slough as part of the new right of way of McKinley Avenue/US 99W/LRN 5 had been awarded.
The 1930 Division of Highways Map City Insert displays the US 99W/US 99E split in Stockton. US 99/LRN 4 is seen entering Stockton southbound via Wilson Way. At the intersection of Wilson Way and Charter Way US 99E/LRN 4 split towards Manteca via Charter Way eastbound and Mariposa Road southbound. US 99W/LRN 5 split towards French Camp via Charter Way westbound and McKinley Avenue (now El Dorado Street) southbound.
During June of 1931 the Division of Highways made a request to the AASHO to extend US 50 from Stockton to Oakland. The AASHO approved US 50 to subsume all of remaining US 48 shortly after the Division of Highways request was made. The extension of US 50 aligned it through Stockton via Wilson Way on a multiplex of US 99 /LRN 4 and onward towards French Camp via what had been US 99W/LRN 5. US 99 south of Wilson Way subsequently reverted to a single mainline route to following what had been US 99E/LRN 4 via Mariposa Road and Hogan Road.
In the August 1934 California Highways & Public Works the Sign State Routes were announced. California State Route 4 ("CA 4") was announced as the highway originating at US 40 and terminating at CA 89 near Ebbetts Pass. CA 4 eastbound originally entered Stockton via LRN 75 on Garwood Ferry Road. CA 4 eastbound multiplexed US 50/LRN 5 on Charter Way from McKinley Avenue east to Wilson Way. From Wilson Way CA 4 eastbound multiplexed US 99/LRN 4 on Mariposa Road and split away at Farmington Road/LRN 75.