Location #1: Cross Roads
Roughly at what is now 11321 National Boulevard, Los Angeles, California, United States
Location #2: Joad farm
This is a studio backlot / movie set
Location #3: Driving through..
Albuquerque, at Central Avenue Southwest & 5th Street Southwest, Albuquerque, New Mexico, United States
Location #4: Then
Main Street, Sayre, Oklahoma, United States
Location #5: Martin’s Service Station
Route 66, Santa Rosa, New Mexico, United States
Location #10 Grapes of Wrath appears to be US 66 inspection station Daggett CA. Santa Fe RR tracks and telegraph lines to the right are a clue. UP RR tracks from Yermo joined up there and on into Barstow and Cajon pass into LA. US 66 and US 91 from Las Vegas followed these tracks. It was modernized a few years later. Now of course I-40 and I-15 are there. Inspections too. But the Joads got across. Excellent site you got here,just found it.
Bob A is right about Location #10. If you take a Google Street View of Route 66 at Daggett/Yermo Road looking west where the old Inspection Station was, you can see the low foot of the hill off to the left same as in the movie photo above. Most people claim that an early version of the still standing Inspection Station east of Daggett on Route 66 was the one used in the movie, but there were never any trees on the south side of the road there.