The May 1925 California Highways & Public Works references state maintenance of LRN 64 along the Mecca-Blythe Highway as beginning on January 1, 1925. Funds for the state to directly assume maintenance of LRN 64 are noted to have been sourced from the 1923 gasoline tax law.
The California State Highway Engineer submitted a recommended routing of US Route 60 to the AASHO Executive Secretary on September 8, 1931. The route description of US Route 60 shows as ending in Los Angeles by way of Pomona at an undisclosed terminus. The routing of US Route 60 defined it as entering Coachella Valley via LRN 64 through Box Canyon to Mecca towards Coachella. From Coachella US Route 60 joined US Route 99/LRN 26 passing through Coachella Valley towards San Gorgonio Pass. At San Gorgonio Pass, US Route 60 split from US Route 99 into the Moreno Valley Badlands via LRN 19. US Route 60 followed LRN 19 west to the vicinity of Pomona where it would rejoin US Route 99 and LRN 26. US Route 60 followed US Route 99 into downtown Los Angeles along LRN 26 where it terminated downtown.
A letter dated June 2, 1939, from the AASHO Executive Secretary to the State Highway engineers of; California, Nevada, Oregon and Idaho noted the proposed alignment of US Route 95 south to Blythe, California. A separate letter to the Nevada State Highway Engineer notes that a last-minute request was made to extend US Route 93 south of Las Vegas to the California State Line via Searchlight over Nevada State Route 5 instead of US Route 95.