LRN 4 through Bakersfield can be seen signed as the Inland Route and National Park-to-Park Highway on the 1920 Clason Highway Map of California.
The original alignment of US 99/LRN 4 through Bakersfield on; Chester Avenue, 19th Street and Union Avenue can be seen on the 1930 Division of Highways Map. Author's Note; I am aware that the Historic Route of US 99 is signed presently on 18th Street in Bakersfield. Thus far I haven't not been able to locate any map source or photos to substantiate US 99 was ever aligned 18th Street. The Kern County Historical Society was the body that posted Historical US Route 99 signs in Bakersfield, their article regarding the topic (which mentions 18th Street) can be found here.
The September 1937 California Highways & Public Works describes 11.7 miles of Union Avenue (US 99/US 399/LRN 4) in Bakersfield south from Grove Street as being expanded to four lanes.
According to CAhighways.org the route west terminus definition of CA 155 changed via 1965 Legislative Chapter 1372 from Bakersfield to Delano. This measure partially annexed the original CA 211 and eliminated former US 99 on Chester Avenue in Bakersfield from the State Highway System. It is unclear when the 1912 and 1942 Chester Avenue Bridges over the Kern River were replaced.
The 1977 Caltrans State Highway Map shows the CA 58 freeway in Bakersfield complete. According to CAhighways.org the route definition of CA 204 changed via 1978 Legislative Chapter 287 to have it originate at CA 58 via Union Avenue. This measure relinquished Brundage Lane from the State Highway System.
CA 204 northbound on Union Avenue is co-signed as CA 99 Business. CA 204/CA 99 Business northbound intersects former CA 204 at Brundage Lane at Postmile KER 2.07.
At Postmile KER 3.07 CA 204/CA 99 Business northbound intersects the 1933 alignment of US 99 at California Avenue. The intersection of Union Avenue and California Avenue was the original location of the Bakersfield Sign (more on that in Part 3).
At Postmile KER 3.62 CA 204/CA 99 Business northbound on Union Avenue intersects the original alignment of US 99 at 19th Street. Presently 18th Street is signed as the main connecting road to the Central District of Bakersfield.
CA 204/CA 99 Business northbound on Golden State Avenue crosses under the CA 178 freeway.
CA 204/CA 99 Business northbound climbs over the Garces Traffic Circle at approximately Postmile KER 4.80.