First actual map reference I've been able to find. The full view map shows A&P Hwy from Quartzite through Ehrenberg then Blythe through Chuckwalla Rd to Shaver Summit then through Shaver Canyon and connecting with US 99 at Mecca, cosigned with Us 99 through Indio Coachella Valley Banning Pass to Los Angeles.
From Jefferson City Post MO - Local Chamber of Commerce
March 7, 1931:
"A letter received by the Chamber of Commerce this morning from H. A. Russell, honorary president of U S. Highway No. 54 Association States that there is great interest- being shown an Kansas and southwestern points in the improvement of ' this highway on account of its new importance as the main highway artery j serving the new vacation 7 land. Rus- isell points out in his letter that U. S. Highway No. 54 from Vaughn, New Mexico to Jefferson City is a part of the Atlantic and Pacific Highway, "the shortest highway with less deserts and less mountains than any other transcontinental highway between New York and Los Angeles." Highway Much Traveled The Atlantic and Pacific Highway is made up of several important U. S. highways, using 50 into Jefferson City from the east, then 54 to Vaughn, New Mexico and U. S. No. 70 from Vaughn west. Inasmuch as U. S. Highway 54 is probably the most important and scenic section of the new transcontinental highway, the association of which Russell is president is strong. ly urging all states through which lit passes to build a concrete highway so that traffic may not be diverted to other concrete highways which do not reach this region of the upper Ozarks. The Chamber of Commerce is cooperating with all cities interested in this new highway and tourist development. LS SFTEfl M Gfll SEDALIA, MO., March 7."